[Timothy]

The only M-3 and M-6 Lights I can find are either Streamlight or Insight Technologies. Are there other brands? The specs. are pretty much the same but Insight has the best price at Cal’s Armory at $248.00. If you have any knowledge about, or experience with these lights I would certainly appreciate your input.

[Logistar]

I don't think this will answer your question but I bought a "Glock Light" and put on my Beretta instead of the M3. There are available for under $100.

I can't really compare it to an M3 but it has worked fine for me so far. Uses 2 CR123s and has a focusable beam.

YMMV