You can find them on the auction sites. You want the kit that contains only a cleaning rod and brush (fixed sight models typically didn't get sight adjustment tools). Back in '66, I believe the brush should have been bronze instead of aluminum (the threaded portion), also.

If you don't have any luck finding the proper kit by itself, you may have to buy an old box that includes the kit and then resell the box you don't need (I've done this and these, too, are found on the auction sites).