West marine or BoatUS
both sell a type that will replace the complete inlet. If the ones that are missing look like the inside lip of a radiator cap, replace them with the type where the covers screw on with a special key. The ones I have on my 34 will get replace as soon as I have a chance (other priorities on the boat right now) because they have a tendency to get loose, and I am afraid the clean water will be contaminated with impurities such as seawater or washdown soapy water. Easy to replace: loosen up the SS collar, unscrew the 3 screws and pry off the old one. Clean and recalk area and install new one. While you're at it, I'd suggest replacing the waste outlet as well as the original one is not compatible with pump-out attachment most marinas use !. Good luck
