Reptile Basics is what I use for all of my adults. Super fast shipping and the racks are ready to ship out at a moments notice.
OR... you can build one yourself for little to nothing. I recently built a very sturdy baby rack for $250 that will house 64 individual baby balls in 6qt tubs... its really how you go about doing it. Take your time and shop around. Go to home-depot and look around at everything they have to offer (materials) as well if you are interested in building one yourself. The heat tape will go under the tubs. If you build one, build it first with spacing for heat tape, then measure how much heat tape you need, and order some of the new THG Heat Tape. Flexwatt is old news.