I keep my milks in 28qt tubs as juveniles/sub-adults and move them into CB-70s once they reach adult size. Pueblan milks are smaller and should do fine in a 28qt unless you have a particularly large individual.

Reptile Basics make great racks, I have two four drawer CB-70 racks from them and couldn't be happier. If they vend at any reptile shows near your area you can arrange to get a four tub model for about the same price as the three tub (no shipping).