Thanks for the reply, louie. I had almost forgotten about the Sandwich Shoppe - I've not been keeping up with this stuff over the last several years.
I don't remember where I ordered the optic from; it was about six months ago. It looked like the right one (they didn't give the dimensions) and was only a few bucks, so I gave it a shot. What I got looked about right, but was much larger - about 30mm wide, as I recall.
Yes, the light is "ancient," but it has proved to be reliable (except for the optics) and, in spite of owning some fifty flashlights, nothing else has been able to take it's place. This includes an unmodified LSH, Arc4 and a few newer lights.
I already upgraded the LED and did try the IMS reflector, but it cracked after I dropped the light the first time. The Fraen has also now cracked, but it took a lot more to do it. Now that, with your help, I've "rediscovered" the Sandwich Shoppe, I'm thinking about trying the aluminum McR-18 reflector. It looks like it will work, but I need to do some research...