SeaLand "Sanipottie" model 965 MSD
A bit more expensive than some others, but best quality. And btw...the "MSD" designation on all portapotties means it's a model that can be permanently installed and fitted for pumpout.The only difference, btw, between a small 2-3 gal portapotty and the larger 5-6 gal models is the height...the footprints are the same and the same hold down brackets can be used if only replacing with the same brand. However, on smaller boats that don't have an enclosed head but only have a portapotty under a settee or berth cushion, the additional height could be a problem. But one that can usually be solved by removing the lid and allowing the cushion to serve as the cover. Since the bowl will be empty the trap in it to the tank closed, it doesn't matter whether the portapotty is covered by a closable lid or only by a cushion. But MEASURE to make sure that will work before buying!