I concur. "Showkeys" reproduction lenses are a good choice. I bought one late last year when I was restoring my 650T. I could not locate a complete assembly, so I cast a base and end cover from my 500T using a plaster of paris mold, and standard fiberglass resin. I have ket the molds, and they are probably good for another 3 or 4 castings. The lens that Showkey sold me fitted-up nicely to my castings. Refer to my earlier post about "Casting" and the pictures on photobucket.com.
Worked out quite well.................