I see ppl selling xmods and mini-z's all the time on Craig's list and ebay, but rarely do I see tracks. Here's a guy with TWO:
http://chicago.craigslist.org/nwi/tag/2398847110.html

Hotbodies Minizilla
 
GPM:
Alloy front damper plate
Alloy Front gear box tower
Titanium complete Tie-rod set
Complete alloy steering assembly
GPM Front Universal Joints
Topcad:
Alloy Front and rear lower A-arms
Alloy Front and rear upper A-arms
Alloy Front and rear oil filled shocks
Alloy Front Shock Towers