If you're looking for 1:1 models, have a look at
Microform Models' 1/16" section. A couple of them are just a touch too long, but clever mounting or a little trimming will take care of that. At less than a buck a piece they're also a ton cheaper than trying to chase down Micro Machines, which now tend to command a small fortune thanks to the original sets being out of print and are now purely a collector's market.
The only real downside is the $20 minimum order, but by the time you get a full compliment of cars [16], you're close...a little bit of scenery to help with the 3D arena, or a few spares to cut up and really push the dystopia and you're there.