Look at stuff that isn't exclusive to guns.

Good pin punches. And other punches.

A big assortment of straight slot screwdriver bits.

Small screws in unusual diameters and pitches. And the taps and dies to go with them.

Clamping fixtures and devices to hold small or unusually shaped parts.

Cleaning supplies like small tube brushes, 1/4 inch and up, in metal and synthetic fibers, stiff and soft. Other styles of brushes too.

Good ultrasonic cleaners and stuff for them.

Finishes for metal. Cold bluing, black oxide, and parkerizing kits. Stuff for polishing metal.

You will be competing with the internet so you want stuff that people will need right now or something they want to see and fondle.

There are people involve in RC modeling that would use some of the same tools and supply's that gun people use. There are hobby machinists making miniature machines and motors also. You might check at places like Colpar Hobbies for information about them.

Good Luck.