This may have come up before but i was wandering aroudn the local Big Lots store today and found this for 5 bucks...
not sure if this is Z-scale...smaller or bigger.... here is a pic with the battery to show a little scale
heh this thing is driven by independant motors in the back wheels like you would drive a tracked vehicle... and the nifty part is when you go forward you get...
they are called Mini Racers. the car takes 2 AAA and the controller takes a 9 volt... thought they were a nifty and cheap change from my own Zaps/Microsizers