What kind are you looking for? The float bob at the end of a cord - I may have a new industrial one to spare c/w counter weight. It is good quality american made. I have one running for over 6 years. Probably around $50 and only if I have a spare as well. Almost nice to ahve a spare in case they fail.
OR are you looking for those fancy little guy that you need to drill into the tank - I have one burried somewhere.