Is it possible to make a casting from a litter box?

I know it sounds gross but hear me out. The litter box is completely clean and fresh, as I had changed it out when my boy started having potty issues. I had placed him in the box to see if he could go but he couldn’t so we went to the vet.
It’s been almost four months, and his little paw prints are still just sitting there. I’m wondering if I could make some type of casting of his prints in the box and turn it into some kind of art piece. Any craft people in here who can give me advice?