T actually wrote the foster father last night and he got back to us with lots of good suggestions. Turns out the litter brand he was using is one of the types we used to use for Nadia and we still have most of a box. So we'll mix it in together, see how that goes.

So here's the complicating factor. Kitty boy is using the box quite happily, no issues. What if we turn everything upside down in order to get the girl to use it and turn him off in the process?