I am not sure of where to actually purchase stackable enclosures, unless u want to order on the net & it can be pretty pricey. If u are looking to stack 3-4 enclosures...a beardie condo would be perfect for u & would probably save u lots of money! lol! Here is a bit of info on them from another forum I am registered at....
FRAME: steel garage-type shelf. It comes with the shelves, all the ceilings and floors are melamine covered particle board, the back is plywood, and the ends are pegboard, one side has like a laminate stuff over it, and they other side is just bare.
Put the shelf together. Then drill holes through the metal frame, big enough for the bolts you chose to fit through, two on each side of each corner, of each section, one higher and one lower.
WALLS: Once it is put together, measured each section’s ends, and back. Cut the four pieces of plywood for the backs, (3/8 inch a/c plywood) and measure all 8 of the ends, and cut those out of pegboard. Put two coats of sealer on both sides of each piece and all edges. (It’s water based, non fumey and non toxic...comes in a turquoise colored can, and it only comes in quarts, it’s by the deck stain at the home improvement stores.) Fit each piece where drilled holes to line up with the holes. Put the bolts through from the inside and put the nuts on the outside, so the ends of the screws won’t be inside the enclosures where the beardies could scrape themselves on them.
LIGHTS: Drill holes through the back wall of each section, to put the wires through for the light fixtures. All the lights come out the back, and are plugged into a surge protector/power strip.
FRONT DOORS: For the front doors use the quarter round nailed on the bottom and top, leaving a space between the two so you can slide the plexiglass.
FINISHING: Clear water based non-silicone tub and tile caulk, and put a bead of it all the way around every crack inside the cage, tile floors, and furniture, let it dry for like 48 hours.
~Sandy