i think i retofited a square lens and bezel from some unknown ford into mine, more/better light and better chrome. but looks like it belongs there.
go one step better and hit the junk yard and look for a late 70's LTD or other big ford and get the dome/map light combo. I pulled several from the yard i goto and i never paid more that about 5 bucks for them. MY . Robert
I have one I bought from Autokrafters a couple years ago, never used it. They changed half way through 1971 so you have to know when your car was built. If you need the one for "before 6-1-71" you can have it for $5 + shipping.
BTW, the lamp that RobertBailey describes is what I have now and they are very nice. You can usually find them on eBay.