stainless steel fabricator

Do you already know what you are doing and able to do it yourself but just want some sheet? Lots of places will on the internet will custom cut all sorts of metals in any shape or size, including stainless. I have used them many times. The cuts are clean and relatively precise, and prices are quite reasonable. You will want 304 stainless, with a brush (#4) finish, if you want to match the stove. I am not clear from the description what you are doing -- is this to extend the backsplash from the stove riser? If so, you should check the specs of the riser for its thickness so you match up.

You can try:

http://www.onlinemetals.com/index.cfm
http://www.metalsdepot.com/index.phtml?aident=
http://www.frigodesign.com/php/splash/scb_splash.php

In Manhattan:

I dont remember the name but go to Christie Street, very resonable. If you go to Houston make a right on Christie its about 2 blocks down on the right.

Go down to the Bowery and walk into the kitchen supply stores. That's what I did. Easy and cheap. You may need to back that stainless with a heat shield depending on what the walls are made of.