How can I modify a toilet seat (ie, add a ledge) so I can potty-train a 3-legged cat?

Toilet-training a cat requires that the cat learn how to perch on the edge of the toilet seat and squat, so this obviously requires good balance. I just adopted a 3-legged kitten and want to potty-train him, but I need to add a ledge-type thing to the side of the toilet seat so he can balance. If it matters–he is missing a hind leg.

Any ideas how I can do this? I’m not super-handy, but I’m willing to put effort towards making this work! Thanks so much for your suggestions!

When you “potty train” a cat/toilet, how in the world does it stretch it’s little legs across toilet seat?

do they accidently fall into the pot a few times b4 learning properly to use the bathroom over a TOILET?
[to those who've been successful training their cat to do this]

Feline Evolution CatSeat Cat Toilet Training Seat, White

• Train your cat to use the toilet, saving you thousands of dollars in litter
• 100% of toilet training is completed on the floor, wherever you choose
• Environmentally friendly litter-free alternative helps keep the Earth clean
• No messy trays or litter boxes to remove
• Keeps germs away from you and your family.

Product Description
The CatSeat saves you thousands of dollars by eliminating litter. The CatSeat is the only product that allows 100% of the training to be completed on the floor in a place that YOU choose. There is no need to sacrifice a bathroom during training. The sleek new design and improved mechanics makes the award winning CatSeat the ‘GREEN’ alternative to filling our landfills with used litter. The CatSeat can be mounted on the toilet using no litter, or it can be used exclusively on the floor in place of the litter-box. Either way it prevents your cat from tracking dirty litter and germs throughout your home.