Good, small cages for robo hamsters?

Hi, I want to get a Robo dwarf hamster soon and I want a not too big cage. I want a small, good cage for hamsters. I was thinking of the habitrail ovo pad, but I heard it has bad ventilation, but I also heard its awesome for a robo. So, is the habitrail ovo pad a good home, or bad? And please give some links for good small cages! Thanks!