74mm scales are kind of a rarity to be honest. Felinevet (a member of this forum) is your best option. Every once in awhile CentralValleywholesale of Ebay has some, but maybe they are stocked "maybe" just a few pairs twice a year.
Might just be better off buying a used/junk SAK with decent scales for transplant or some custom scales.
If it were any other size (short of 108mm) you'd be able to get scales pretty easy...