You would have to separate the cats. The best thing to do would be to put Bo in a room with the litter box and no litter in it. Some cats will urinate in the box even without litter in it. If he does then just pour it into a container and bring it in. If that doesn't work, the vet has NoSorb. You are right, they are beads you put in the box that the urine will not attach to. All you do is put the NoSorb in the empty box just as you would regular litter. Then when the cat urinates, just pour the urine back into the cup that the NoSorb was in and bring it to the vets. If that doesn't work then you will have to bring Bo into the vets so they can try to express his bladder there.