Fashlight adapter
USB laser sight 
11, 20 and 21mm dovetail adapters.
Red is most economical
Green for improved daylight.
Blue for enhanced daylight visibility or for those with red green color blindness. Blue lasers in general use a third less power. Results vary in regards to application. It is said that it is less likely to be seen by the target in many situations.
TEMU low
Temu II
Use the press fit or you can glue with a PETG to Metal glue as in epoxies like
JB Weld or Weld-on 16
PC-7, Hercules, KBS New Metal, and Quick Steel, as well as Loctite products,
Gorilla Glue, and specialty adhesives like 3M Panel Bond and West Systems epoxy
Loctite 435 (a cyanoacrylate) paired with Loctite SF770 activator
Loctite Epoxy General Purpose
Light Sanding