Their is a touch up blueing pen if small that might work and no be noticeable. Or go on the KT boards and find address of guy that does the HC of the slide around 30 bucks You just send slide.
Me I just use a sharpie and touch up Carry guns get wear
"Just say "Lay A Way"
"WWJBD" What Would James Bond Do?
"Hokey religions and plastic glocks are no match for a good 1911 at your side, kid."