The Carclo 10025 will fit in a Mag. (available from Cutter.com.au)
It's a different kind of optic though; it has a metallized rear surface and it's proportionally much shallower than typical TIR optics.
You won't find a production TIR optic 50mm in diameter. It would be very heavy (about 15 times as heavy as a 20mm dis optic thanks to the laws of scaling) and probably quite expensive.
Three Khatod-style optics will fit in a Mag head.