Could you just get a second 8 panel ex-pen and fold the excess out of the way? I’ve found they are pretty easy to tie together using zip ties

Thor’s idea is a good one, you can also overlap the two pens and connect them with dog leash type connectors or binder ring type connectors that are easy to take apart and made out of metal your bun cant chew. If you do this you can also easily detach the second pen to take outside for playtime, or you can use it to put two pens side by side in the instance that you get another bunny and need seperate housing for bonding. In the long run more pens are always useful… I’ve seen them on amazon in 36 inch height for $35-40. For you, since you already have one pen, that would be a pretty affordable idea.

For floors I used to have an x pen and I just used sheets as the floor, rolled up the outer edges along the outside of the cage. it worked really well for me, but I had a bunny that never peed on the floor so waterproof didn’t matter. I saw an idea on 101rabbits I liked where she used puzzle excersize mats and covered those with fleece throws that could be easily thrown in the wash but I don’t see how this is easier than throwing a sheet in the wash or a fleece over a tarp in the wash. You can get twin sheets at walmart for pretty cheap, I think $10 or maybe even a bit less for the basic ones. If you got a couple you could just switch them out when they got dirty and throw the other one in the wash easilly.

When I get my new bunnies I decided to build a NIC pen, for a couple reasons. The set of 69 squares is 66 dollars, but with that I can make a huge pen, mave extra for making dens, baby gates, bunnyproofing, ect. If my buny situation changes, I can move around these squares to temporarily make 2 smaller pens. And by making a pen I can easily take it outside or move it to another room. I plan on using sheets for flooring again, or 50×60 fleece throws I can get at walmart for $3 since the pen will be 42×56 inches (3×4 NIC squares.) Im going to try the fleece first, if it doesn’t work Ill do the sheets and if he’s really messy Ill put a tarp peice under the sheets or try the puzzle mats… but hoping this bun is like the last and not too wet messy.

I don’t reccomend an NIC condo… I built one once and it was big and nice but ultimately a pain in the rear end to clean. Once I switched to a pen… I knew Id never go back. My bunny didnt chew the zip ties, but Im sure you have a good reason for thinking your bunny will. If you put the pointy or big part on the outside maybe there wont be enough for him to get a hold of. Good luck (Geez I wrote a lot. )