I use a Japanese version of this type of box. It's the same concept, but the litter is made of cypress wood shaped into rather large pellets, and the liner underneath is made of disposable cypress pressed wood boards. I love it! The pee goes right through, so clean up is so much easier. I just stir the litter a couple of times a day and scoop out any poo. Best of all, there is no dust or tracking. That was the main reason that I switched to this type of box; trying to reduce the amount of dust to ease Sammy's allergies.
Sammy's about 11 pounds, and the box is just the right size; it's 57 x 43 cm (22 x 16 inches). I took the side guard off, since Sammy didn't seem to like it.
Here's the product page, just to give you an idea
The litter is larger than normal, so it took a while to transition. At first Sammy refused to use the new box. So I put her regular box back, and added a handful of the cypress pellets to her usual litter. She didn't seem to mind, and used her box as usual. I gradually increased the amount of cypress pellets in her litter box, then finally switched to the new box, and success!! Sammy is using the new box exclusively!
I like Carl's idea of using a washable diaper to save costs on pee pad replacements, and may give that a try. Although Sammy is OTJ, she still pees quite a bit because of her CKD. The cypress pee pad is supposed to last a week, but I've been changing it every 3 days or so. The litter also needs to be replaced every week. With crystal litter, you could probably wash it and reuse.