Terminator Miniature Help needed

Hi All!

My gaming group and I are busy doing up rules for the Terminator Furture
War 
genre in Stargrunt and Dirtside and are getting to stage of testing them
out. 
 Now we can represent the Human Resistance forces pretty easily (just
going 
to use some kitbashed pickups and the NAC as troopers) and we've got a
line 
on some endoskeleton minis but the SkyNet heavier units are a little
harder.

Does anyone here know if anyone makes 6mm and/or 25mm minis similar to
the 
big HK Ground Tank and the Aerial HK units?  If not, can anyone suggest
some 
alternatives, give tips on kitbashing them or tell me somewhere I can
look 
for tips on how to kitbash them?

Thanks very much for your time.

-Kelvin....