Hamilton Marine is the best place I have found for the Ultra Pumpswitches (non-alarm). I have bought them for as little as $99 on sale there, and price right now is $119.
It's just one of those things I feel that buying the best is the way to go. In addition to being extremely well built and wired, and easy to install, they don't short cycle, they deal with shower and sink sludge well, they have a lamp that indicates whether the system has electricity. So they take good care of the pump in a few ways while they are at it.
As for sump pumps, since we lived aboard full time, I just used, as did the PO, standard Rule 2000 bilge pumps. Sounds like overkill, and it is for most boat designs, but on our Hatteras, the 3 sumps were designed in such a way as to act as high water backups to 3 of the bilges. If not for that i would likely have used something in the 1000gph range, but dang those things drained in a jiffy. Strainers over the shower drains, and a regular dose of distilled vinegar kept things running smoothly with very heavy use.
"There's the Right Way, the Wrong Way, and what some guy says he's gotten away with"