Lowes, Home Depot or any plumbing supply
In pressurized water systems, a faucet is a faucet, and the plumbing sizes are all the same, whether on a boat, in an RV or in a house--nothing "marine" or "RV" about 'em. Go with the best quality if you want to last more than a few years in a salt air environment.Unfortunately, though, you're stuck with a marine supply source if you have to replace manual hand or foot pump fixtures.