I hope you can find someone to do this... but if you can't, there's always a file (or a Dremel if you're confident enough). I've brought down reflectors with both. :shrug: All you need is a steady hand, and a little bit of patience.
Sandpaper is your friend. Start with a course grit and start changing to finer grits as you get closer to your target length. Rotate the reflector as you go, and work on a level surface.
IT'S DONE! I finished my TIR to Reflector convert. I sanded a shaved down McR-19 XR reflector and put a UCL lens. And now that your interested. 100x Thanks to TranquillityBase for providing the the McR-19 XR.