There are a couple options.
GG&G and Midewest industries make short sections of 1913 rail that “sandwich” the A frame front sight base. Use thread locker and witness mark the screws. Had this on an issued work M4 for several years. It works.
Another, slightly better option is the Impact Weapon Components mounts for GI Handguards. It’s a cantilever type mount which attaches vis the cooling holes on the top of the handguard. The mount is reversible and can be used to mount the light on the left or right. It is a direct mount to the scout light. There is also a version with a 1” ring for hand held lights.
https://www.impactweaponscomponents....ry/ar15-m4-a2/
Third option is Arisaka makes a version of the Hanen mount that allows mounting of a pistol light such as the X300U and TLR-1 on the front of the A frame.