i have searched on different occasions over the last several months for an rv shower pan & toilet combo, like i've seen in the newer airstreams with wet baths with no success.
well, just when i thought i exhausted everything and figured i'd have to get a shower pan from ppl motorhomes and build the toilet base and somehow waterproof that, i'm happy to report i finally found a source;
Shower Pan/Tub-Toliet Mount
thought some members may be looking for the same thing.
it's a very happy day!