Interesting. Do they have to be seated or are you chopping them off at the waist? I've painted hundreds of 25-32mm figs over the hears and not seen alot of seated 28mm figs.
If you're chopping them anyway, Reaper has alot of possibilities in their Chronoscope line (modern and sci-fi figs) and they're not terribly expensive in their "Bones" (vinyl) material. They're a bit bigger in 30-32mm (sole to eye) though. I might have a few extras lying around from some kickstarters I could let go cheap...
Still, if you're going to chop and put them in cars, second hand Heroclix for a buck or less are probably a cheaper alternative.
I was looking for seated, full figures and only saw a couple, but still looking.