Microscale made a US armor sheet many moons ago in 1/35, but I dont know if they do any armor decals any more. Try Bison Decals, they have a large line of US, UK, German, French, etc. armor of most eras currently available.
Here is a link to their 1/35 product listing:
http://www.angelfire.com/pro/bison/35.html
F is for FIRE, That burns down the whole town!
U is for URANIUM... BOMBS!
N is for NO SURVIVORS...
- Plankton
LSM