You can scavenge the parts from the mini fridge and just build it all into a smaller insulated box. Most mini fridges don't have anything but foam in the sides you could simply cut the thing in half down the middle and take out some of the depth and then just toss it back together with some flashing and construction adhesive.
You could also put a tank of water in your kitchen fridge and pump water through a coil in an insulated box that's just big enough to fit a corny keg or two.
Check out the DIY Forum there's a lot of custom kegerator builds over there.
You may however just want to leave the kegerator in the garage. I keep 4 kegs on tap in the basement, and sometimes I'm in need of more cooler space for kegs. I currently have a 4 tap kegerator, and two mini fridges, one to ferment and one to keep 2 kegs ready to go in the kegerator. I wouldn't want to lose that space in my kitchen.