The Car Wars scale car, cycle, and truck counters in GURPS Autoduel appeared in various Car Wars products. The scaled-up ones are simply scaled up versions of the green and red cars on the top row in the picture at the link you posted.
There are similarly scaled up counters in Autoduel Champions.
Michael "owenmp" Owen might be along shortly with some of the same info I'm about to present, but you can get a ridiculous amount of counters directly from SJ Games in the following products:
Car Wars Expansion Set 1 - Road Sections and Counters
Car Wars Expansion Set 2
Car Wars Expansion Set 6 - AADA Vehicle Guide Counters. In black and white, so you can print 'em out by the millions and color them -- or Photoshop them in color and then print 'em out -- to your heart's content.
Car Wars Deluxe Edition or
Car Wars Deluxe Edition (Car Wars Compendium Upgrade). The latter is if you already have the Car Wars Compendium; the former is if you don't. Includes lots and lots and lots of counters...