Please understand, I have zero interest in promoting one source or knocking another, BUT... Those clearance lights from m4 are single wire. At a minimum, call the owner. Should be easy per above posts. Ask how those get grounded. Reliably, without a ton of extra work. I'm sure from those same posts that m4 offers good quality and service. Again, BUT... the "RV" lighting assemblies (including clearance) look like truck items moved to the RV Aisle.
Here's another example of a two-wire LED clearance light, this time from a known manufacturer (who may well get them from China like most of the rest...)
Bargman LED Eastern Marine