Another inexpensive small knives are Ruike's S collection, blades are 53mm.. so close to the limit, maybe over to the pivot and require modification.
No idea how reliable fenix outfitters (I'm wrong side of the pond) are but seems to have a sale on...
https://www.fenixoutfitters.com/fenix-ruike-knife-s31-stainless/Knife, scissors, screwdriver/hook/cap lifter tool for $15 so wouldn't get too broken up about it being confiscated.