So I tried my luck at evil Walmart. Hit the jackpot there. So I bought some regular kitty litter and snagged a bunch of boxes for them.
And yesterday they started using their new box! It was so exciting! The little one (whose parts are starting to look like boy parts) ate some kitten gooshy food. The big one continued to have formula. He doesn't seem to dig the solid stuff so far. I think I will try to entice him with some tuna mixed in to some kitty mush.
Today they are very, very playful. Scampering and rolling and wrestling. Awww!