I had one of them on my 71 Caravel, and although I never had to replace it, I can't recall ever seeing one like it in any of the RV parts places or catalogs I have seen. But one of the speciality suppliers, such as Inland RV or Vintage Trailer supply might have one. I would give them a call. Andy at Inland RV has a huge supply of things not shown on his website, so don't just look there, call him.
It's good to know I'm not going crazy. I can find what seems to be a marine equivalent - for $30-$50 so I may just buy it anyway to see if I can make it fit..
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