Automatic Litterbox Central

I have one very spoiled kitty that loves her CG litter box. I on the other hand see it as an opportunity to get close to my hacker side. Like many I have read here I need to find less expensive ways to make it all work, though I must admit not dealing with a litter box in the normal sense is FAB!
Looking for a replacement for the pellets CG uses. I'm lucky my little ninja kitty doesn't get them every where (one box in a years time is good from what I've read)
See ya in the world!