Whenever NEMA heads show up on eBay, they never come with the optical assembly. The optical assemblies are supposed to be common, but I have searched far and wide and I haven't been able to find one for a good price. (I know there are some Hubbell ones on eBay right now, but I'm not paying $50 for one of those!)

Does anybody know where I can get them?

I know what you mean! I need four of them right now!

Ironically I have a Revere gumball optical but without a NEMA head for it. It's currently mated to a old Landmark yard light head but I was thinking of getting a Cooper RMA head for it.

If you are still looking for some, this guy still has a few: https://www.ebay.com/itm/364322026303

Thanks!