Possibly get an assortment of Hardened Washers.

I bought some, a few years ago, and they are less expensive than CAT hardened washers, but their OD is bigger than CAT and their thickness is slightly thinner.

 It is still nice to have them , on-hand.

 Sometimes, a CAT hardened washer "fits" better, in tight situations, with its smaller OD.

Note: I always have lots of the cheap "Hardware store washers" on hand, also; but there are certain areas, where you want hardened washers, that don't bow inward, under a hard load.