I went with a ShurFlo revolution pump. I know you said you don't use your pump at all or very rarely. I don't use mine much either but, I was able to get the upgraded Revolution pump cheaper than the standard pump. I can't believe how quiet it is. I'd say it is about 80% quieter than a standard water pump.
They do also sell check valves for water pumps. Just check the plumbing sections on alot of camping store websites, such as the link below. Obviously, if your pump head shows signs of leakage then you'll have to replace it.
Pumps Fittings on Sale! - Adventure RV