Portapotties aren't that convenient.
If you want to stay out more than just overnight, you'd need a 5-6 model...which would have to be an "MSD" version that's permanently installed and fitted for pumpout 'cuz most marinas on the Bay don't have portapotty dump stations and won't allow you to dump 'em down the toilets in their rest rooms. But even if you could find a place to carry it off the boat, a full 5-6 tank weighs about 50 lbs.
So my advice...learn how to manage a decent quality toilet and tank, 'cuz when done right, it's no more inconvenient than what you THINK a portapotty would be.