Is this the one you found in a dumpster? It looks like a Norelco judging by the shinier area where a tag would be and the smooth reflector. You can probably buy a new reflector on eBay if you do some digging or you could also order one through your city and then put the plastic on this old reflector. They generally have a metal band wrapping around the bottom lip of them but yours may have lost it so you might have to borrow it off the new bucket if you order one.
The reflector is from the fixture I found at the dump but the rest of it is a Landmark 175w MV that I converted to 100w MV using a 70w MH ballast.
Here is a pic of the NEMA head I found at the dump. Is that the ring your talking about?
I have thought about asking my local electrical utility company (Hydro One) for old fixtures,lamps and ballasts but not quite sure how to go about it lol.
Do you really think that my city could get one of these for me? Never thought about doing that before.
Thanks