Reddit mentions of Whitmor Storage Cubes - Stackable Interlocking Wire Shelves - White (Set of 6)

Sure thing!
https://www.amazon.com/gp/aw/d/B007ELAS9G?psc=1&ref=ppx_pop_mob_b_asin_title

I highly recommend purchasing zip ties to help strengthen the intersections between each side. An amazon reviewer suggested it in their product video and it seemed to help a lot!

It's those panels used to make storage cubes.
https://www.amazon.ca/gp/product/B007ELAS9G/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

It's all assembled with zip ties, including the levels :) There's lots of tutorials online!

I used these. It comes with 23 grids, so you might need more than one pack depending on what your plans are. I used the included connectors plus zip ties to hold it all together. The base on the upper level is corrugated plastic covered in self adhesive carpet tiles.

Not sure what your budget is or what type of cage you have but I used these type of wire cubes to built a bigger home for my bun. For ideas on how to make a door/entrance take a look at this thread from a few weeks ago.


You can also try to put mats against the wires so he doesn't chew the wires and gets a snack instead. If he doesn't pay much attention to the mats you can try what I do at times, I get the treats (see link below) and rub it against the mats so it's more a more appetizing snack.

A few other suggestions when you move and have bigger space:

• Tunnels - Options 1 - for this one just keep an eye on the hanging ball - my bun chewed right through the string to get rid of the ball but otherwise loves the tunnel, Option 2, Option 3
  
  Treats (recommended by her vet)
  
  I also agree with a lot of the suggestions here, I have the Living World Teach treat toy and my bun just loves it, though doesn't care for other toys but lives for cardboard boxes. Hope this helps!

Copy and pasting this from another post of mine:

   

Target, Walmart, or Amazon. Same brand and about $30 shipped from all three. For Walmart and Target specifically, there's no shipping charge if you choose the in-store delivery option. Or check if they sell them in-store directly, mine don't.
   

   

The coroplast should be available for about $23 + tax at Home Depot (enter your zip to check availability) for a 48x96 sheet, or alternatively check with local sign shops or plastics distributors, they may be slightly cheaper and have other colors. Home Depot only has it in white.

It's this one that used to be $18, so I got 3 of them and built a 4x5.