I find the DJI Phantom battery to hardly last 10 mins or so. I can't find the battery in stock anywhere. Any idea from where to buy? Is there any alternate battery for this?

10 minutes is normal.
the battery is a 3S (3 cells in serial) at 2200mAH and should be able to sustain 25C (25x the unity Amps of the battery). Then connector is a XT60
So, any cell with these specs should fit, provided the size is ok too.
I ordered a 2700mAH , and it is ok, but you can hardly close the door. Some people attach the battery or a second one under the body.
You can find equivalent battery to the orginal one for less money, particularly from the brand TURNIGY

I don't have a Phantom but I fly multi's. If your getting 10 minutes of flight time and still have about 20% charge left in the battery, that's about what I might expect.

If you want your Lipo batteries to last you need to make sure that you don't over discharge them and charge them correctly.

I don't know which battery your using, I doubt DJI would have created a battery specifically for the Phantom, of coarse I wouldn't rule out their stupidity.

Here's a link to HobbyKing, they have just about every battery known to the RC world, keep in mind they're in China and it can sometimes take a couple of weeks to receive your order.

Batteries & Accessories>30C Discharge (http://www.hobbyking.com/hobbyking/store/uh_listCategoriesAndProducts.asp?idCategory=241&LiPoConfig=4&sortlist=&CatSortOrder=desc)

I don't have a Phantom but I fly multi's. If your getting 10 minutes of flight time and still have about 20% charge left in the battery, that's about what I might expect.

If you want your Lipo batteries to last you need to make sure that you don't over discharge them and charge them correctly.

I don't know which battery your using, I doubt DJI would have created a battery specifically for the Phantom, of coarse I wouldn't rule out their stupidity.

Here's a link to HobbyKing, they have just about every battery known to the RC world, keep in mind they're in China and it can sometimes take a couple of weeks to receive your order.

Batteries & Accessories>30C Discharge (http://www.hobbyking.com/hobbyking/store/uh_listCategoriesAndProducts.asp?idCategory=241&LiPoConfig=4&sortlist=&CatSortOrder=desc)

Yep, exactly.

I've been playing around with RC planes and helicopters for years, and 10 minutes flight time is about the most I've ever had from various different models.

There's always the option of a bigger battery, but the extra weight will effect flight characteristics. Best option is to buy a few spare official DJI batteries, or find one from Hobby King with the same or a similar power output and weight.

I switched my DJI NAZA to 4S and it flies much better. I don't know what ESC's the Phantom comes with but I would think 4S should work.

My dealer turned me on to these Hyperion 3s/11.1v 25c 2500Ah for my phantom
where as I believe the stock unit is 2200mAh 20c

To calculate the available draw, Multiply the 25c x 2500mAh and compare the 20 x 2200 and you will see there is a big mathematical difference
Craft seems snappier on take off
The battery is a tad larger but does fit in the battery bay and weigh in at 210g vs 180g for the stock
the extra omph costs more to0 at around 45.00 with the proper connector attached

you cannot multiply the C factor by the unity amps, it is meaningless.
the C factor explains how much maximum current you can burn instantly.
if your battery is 1 amp per Hour (1000mAH), that is the C unit.
Since the capacity is based on 1 hours, you can get 1 amp during 1 hours
But you can also get 2 Amps during 30 min, or 4 Amps during 15 minutes.
Obvioulsy you can imagine there is a limit on the maximum current and time.
Just short the contact of a battery and you will see what happens when a battery works at 100C.
Additionaly, there is also a decrease of power available when you discharge a battery fast.
a 12V 2A battery will give you 24W for 1 hour, but if you draw the battery faster , you will get only 20W for example).

if the battery is rated 20C, it means you can draw 20Amps instantly.
If you draw more, you will probably destroy the battery or the voltage will simply drastically drop.

The C factor is also used for charging the battery. Usually it is C/10 or C/14., so at 1C you can charge the battery in 1 hour, at C/10, you need 10 hours.
Lipo can be charged as fast a 1C or even 3C, so at 3C you will need only 20 minutes.
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Merci pour l'explanation
Generally though a larger c # plus a larger mAh # is better non?

larger mAh will give you longer flight.
bigger C will give you faster climb or speed , more nervous flight.
usually the reference is the C you get on the ESC (the card that drives the motor).
if you get a 30C card you can expect the card could draw as much as 30C, so if your battery is only 25C, you could damage it (sucking too much current, makes it hot) or making the voltage drop too much, loosing power in the motor.
If your card are 30C but yout battery is 35C, you should not see any improvement until the battery is almost totally depleted. At this stage, a high C battery should be able to provide more residual current than a lower C battery.