Amazon has a plethora to wade through, and they are very cheap. But buy extra - in the two dozen I bought, several failed right away. Some of the others have bases that are intermittent in making contact in the sockets, so judicious tweaking of the contacts got them going. So, some futzing - but since I save a huge amount of $$, it seems like a decent trade off.
2012 Ford F-150 Eco, Max/Max
Jayco 26.5 RLS, Reese Sidewinder