Go on line and query subjects, such as, "petcages, animal cages, rabbit cages, rabbit supplies, rabbit accessories"and the like, in order to get some idea of what is out there.Rabbit supply houses will sell you materials/tools to build yourown. The American Rabbit Breeders Association site has plansfor rabbit housing, as do other such sites.
I make extremely functional and user friendly rabbit cages from dogcrates we purchase at yard sales and flea markets for nominalsums. I make a wooden frame of 1" x 3" pine, with1/2 x 1/2" vinyl clad hardware cloth(wire) attached, that I suspendinside the dog crate with hardware hooks above the slide in/out tray.
The beauty of this conversion is that the door is easily opened, yetcan be securely closed; the top swings openforeasier cleaning and maintenance; the dog crate is tall enoughto permit bunny to stand up; crates tend to be roomy and substantiallyconstructed; crates can be easily disassembled forstorage purposes; and, purchased at yard sales and fleamarkets, tend to be incredibly inexpensive. For me, such aset-up, including crate, cost of lumber and hardware clothusuallyis no more than $20.00 maximum.