Does anyone know where I can find a replacement lens cap for the XL1s? I'm using an old 35mm cap for a 72mm lens, and its cumbersome to get on and off because the grips are not in the center. I've searched on the net but can't seem to find anything, and my local camera stores around here don't have just a replacement cap. Any ideas?

You could call the Canon toll-free number navigate to the parts section and order one from Canon - probably not cheap.
Believe the part number of the cap for the standard XL1 lens is something like:
CAP, LENS, YF1-0008-000 000.

Or you can go to a Photography store and buy a regular 72mm lens cap that will fit just fine.

This is probably more than you're asking for, but as with all things Porta-Brace, this is a killer accessory.

http://www.portabrace.com/product_detail_A.php?id=311

Hope it helps.

Your link doesn't work, but is this what you're referring to?

http://www.portabrace.com/product_detail_A.php?id=3117

have you used this before? Would you recommend it?

Sorry, I rushed to copy the link and apparently missed the last number.
Yes, this is exactly the product to which I was referring and a) no. I have not used it as it has just been released. But, b), I own many Porta Brace products and not one of them has EVER been less than excellent and they all perform perfectly, and usually better than advertised. These folks do their homework and make this stuff right there in Vermont, a needle's toss away...excellent workpersonship and quality control. And, c), no, I do not work for them, nor have I ever received any of their products for free or less than
retail...unfortunately. d) I am ordering one for myself, as I most of my work is in the harsh and unpredictable year-around weather of the Rockies; less than studio conditions to be certain.

I've just got a Hama standard 72mm lens as replacement fro my original and it works absolutely fine, with a similar locking system to the Canon one. £4 here in the UK