FAK in wallet...I carry a tri fold nylon wallet with velcro closure, so is somewhat adaptable...I've pared the contents to....
water pouch (vacuum sealer bag)
4 water purification tabs
sealed 2x2 bloodstopper gauze
2 2x2 non adherent pads
2 cloth knuckle bandaids
2' duct tape

without adding too much bulk

a 4 x 2 1/2 x 1 generic multi tool pouch holds small Leatherman,Streamlight 110 lumen, fire steel, hacksaw blade, needle, safety pins...slightly wider or thinner material and the Bic would fit also (was replaced by the Streamlight)

key ring...P38,Fenix E01,brass whistle, and a pill fob for aspirin, immodium, ibuprofen

I carry a larger axis lock Benchmade in front pocket, and older Motorola Razr phone on belt...

the additional multi tool pouch is not too obtrusive in a workplace...much less than a pocket clip from a folder would have been in a public high school