That's going to be a tough order, if you are looking for a 'mini' fridge. All of the ones in that size/shape that I have seen that can take a 1/2 barrel are commercial kegerators, and more expensive.
That being said, check craigslist for things like used commercial merchandizing fridges. They come in all sizes and don't usually have the compressor 'hump' taking up floor space. They are often more expensive, but if you are patient you can find them cheap. Good luck, and enjoy your beer.