Well, thanks to cats becoming so popular, now you can create any number of hidden litter box options in your house. (cat-lovers-only.com)
If, as you're contemplating litter box options, you've also yet to decide on a litter, we have a post discussing the best litter brands here. (heavy.com)
Or can you provide additional litter box options for your senior cat? (parkanimalhospital.com)