I lost the foam that goes on the mic of my a1u.
Sorry I don't know the real word.
1-does it make a big difference with foam or without?
2-is it expensive to replace?
3-is it long to receive?

Basically it's just a wind screen, good for outdoor use in wind. I imagine it isn't expensive to replace, although I would assume you would need to get the right fit from Sony directly.

have you need service from sony canada, and since the a1u is a pro camera do they give the service I should expect?
Sorry if my sentence are not perfect because I speak french.

No I have never had to have it serviced...I have only had mine since May 20th 2007.

I would expect that if you brought it to the place you bought it, you should get good service

thank you
and I will keep you informed on this story.

Sony A1u shotgun mic is ecm-nv1.
You are looking for the foam windscreen.
If you shoot where there is no wind (e.g. indoors), You likely won't miss it. Foam windscrrens are really only effective up to a light breeze, after that you ave to find something better. Also depends on wind direction too.

You may be able to find an aftermarket, though I don't recall the dimensions. Here's some examples:
http://www.bhphotovideo.com/bnh/controller/home?O=search&A=search&Q=&ci=0&sb=ps&sq=desc&ac=&bsi=&ci=8651

PS The Rycote softie may be a very nice replacement, if you don't mind the price.