Modkat® XL Litter Box, Top or Front-Entry Configurable, Full Height Seamless Base, Reusable Litter Liners, Sifting Litter Scoop, 2X Bamboo Charcoal Filters - White

We got the Modkat XL for our two ragdolls. It's pricey, but works well, and the cats have no problem using it. Not sure if it would keep out your dog, but you can check the details here: https://a.co/d/01vr1r87