Tracked Armor in the US- Semi OT

[Rockwolf66]

Well I have a question that while the reason I am asking it is Off Topic the information is highly applicable to a TW2K game. I write fiction for fun and hopefully someday profit. I have just gotten a request for a story about a character who is a Merc with some armored training. Basically the character has done a big job for someone in the US government and in lieu of payment they get tracked armor. Now the Question is:

What tracked armor is available in the US?

While I am sure the US can get it's hands on and Import quite a bit. the armor in question is something that was just rusting away at the back of a depot. it could be US armor or it could have been something acquired for testing.

Basically I am asking for research help that is applicable to a TW2K game.