Have you ever seen an old telephoto lens? They still make them, and basically the setup is a catadioptric. The Carclo lens just adds a TIR element (actually, two TIR elements). I don’t see an issue making this out of two pieces instead of one.
The HID spotlights I refer to have what seems to be a spun and coated reflector. The aperture is threaded to allow focus against a stationary bulb. The reflectors themselves as replacement parts are not expensive, and in fact one of them made #3 on Enderman’s list, so it can’t be too bad.
Lot of concern about lens/reflector mounting. That’s thinking backwards. If you’re designing from the ground up, you first have to decide how large you want the optic to be, then figure in mounting (i.e. shelf, lip, etc.) and make it that way. If you’re doing it with an off-the shelf part it’s a different story. Even then if we know that there’s a certain amount of inaccuracy toward the farthest edge of a particular optic, you then make the conscious decision of whether to use the “usable” portion of the lens, or use the entire lens and deal with whatever anomalies you get in the beam, in exchange for a slight performance gain. There’s a difference between taking an off-the-shelf part, and getting the most out of it, versus designing something from the ground up that’s optimized for your needs.
I cannot remember the brand, but there already exists a flashlight head that has the reflector machined into it (as well as cooling fins on the exterior).