Welcome!!! I built my 2 buns a custom condo. its 2 floors and I built It specifically to fit a nook in our house. they free roam when we are home but I wanted them to have a big place to play while I’m at work. We built it out of wood. it ended up costing about 100 us dollars in the end. We framed with wood and the walls are caging. it was a lot of work but is better than anything we could buy and even if we did find something premade like ours it would cost well over what we paid to build it.
However, lots of people use CC cubes. theyre just wire cubes that you zip tie together in whatever shape you want. Just google bunny condo CC
as for the pee problem- you may not need a covered one. they make litter boxes with high sides. specifically the corner litter boxes have super tall sides and it would be easier to fit in their current cage if it worked.
Be careful with the carpet- the fibers can cause a bunny tummy blockage! that being said- a lot of buns like to “remodel” their human’s homes. Make sure they have lots of bunny safe things to chew on. You can also teach your buns they cannot do that. My boy listens very well with just a “no bun, no do!” but daisy is a little more stubborn. we use a spray bottle with water for her. just be careful not to aim for the ears or eyes. But Obviously if you keep the house super cool you don’t want a damp bun catching a cold!
I’m glad you didn’t decide to rehome them! it can be super stressful in the beginning but most buns will learn over time what they can and cant do. oh and are they both spayed? desexing can sometimes calm the destructive behavior.
oh and ps- DOUBLE MANED lion heads sounds super cute!