After doing hours of research I've found what I think might be best for Amy and her health. Amy is excellent as far as the litter box is concerned so if your cat is as well this might be for you.
I've chosen to use a stainless steel box:
dimensions: 20" x 12" x 6"
- Extremely hygenic
- Environmentally friendly
- Does not retain odor
- Smooth easy to clean surface
- Does not require heavy cleaning agents
- Scratch, crack, and rust resistant
- Last forever
- Might not be deep enough for messy diggers or cats that stand to pee
- Can make a clinking noise that can scare some cats
- Not easy to buy - The box is actually a steam table/hotel pan
Use a fully stainless steel scoop that is easy to clean:
I fill it with 3" of litter. Scoop when necessary, and throw it in an odor-proof container. Like a Maxwell Coffee tin. I put the scoop inside of it after. On garbage day I'll empty its contents into the garbage and wash the tin and scoop with baking soda and a tiny bit of dish liquid. The washing process takes only a minute or less. Use a pinch of bleach and let sit for 1 minute if you want to completely sanitize the box of all germs.
Once again, I'm no expert. This is just an idea of mine that might peak someones interest.