Brock is the only supplier of EZ fittings that I know of. Spruce or Wicks has
everything else.
Check the Canard Pushers, I believe that Burt OK'd Grade 8 bolts at one point for the Varieze wing
attach fittings.The flight loads are carried by the cup and the bolt is just there to keep the cups snug.
Do not try to cut longer threads on AN bolts as they can fail where the new threads are cut.