In answer to your question RE a higher quality replacement that has a built-in switch, that also has about the same or larger footprint, no I'm not aware of one. Not to say there isn't, but I've spent no time looking yet. The SPST switch is also very common, and I have seen them with clear flexible covers that would help somewhat from dust and direct water spray. Problem is the pigtails to it are very short and you'd need to pull the whole assembly off to replace it, which isn't that big a deal, but more effort and time required than at the time I looked into the issue.
I did manage to get enough contact cleaner into it (switch) to make it currently work ~80% of the time. Assuming you're in Seattle, humidity is a problem, and the contacts inside are not the type that hold up well in those conditions.
Switch should be located inside the camper, but that would require wiring effort and cost, cutting into FWC's tight margins. 
