The BinkyBunny store sells litter screens (availability may be limited, but it can give you an idea).

A DIY option is using plastic knitting mesh/canvas and cutting it to fit.
Of note, sometimes the high-sided litterboxes can encourage some rabbits to dig because it creates essentially a funnel of endless digging — you could try removing the transparent top half (if possible) and seeing if the digging behavior still occurs with lower sides.

Yep, I think I just replied to this same question in the other thread. I don’t use a grid but I do use a screen. Make sure the grid isn’t hard on her feet, as it can lead to hock issues and also discourage her from using the box.

At the rescue I volunteered at, they only used hay as litter. We would add a bunch of hay to the litter box and fluff it up. The buns pick through and get the good pieces. For cleaning we would dump the whole thing and spray them down daily. This was sort of a simplifying and cost-saving thing for when you are cleaning 80 litter trays each day (!), but it works well if you have lots of hay available to you (or run out of litter!). It’s not the best for odor control though, and you do really need to clean the box daily since there isn’t anything absorbing the pee.

It’s OK to experiment a bit to see what works best for your bun. There are often trade-offs with how neat and tidy it looks and how willing a bun is to actually use the box! And having a grid may help keep the waste away from her, but it’s also hard on their feet. I’ve had really good success with a thin layer of litter (I use pine pellets), topped with a layer of hay, and then a hay rack. I like using screens as well when I have a bun that gets obsessed with digging.