The wiper pivot seal kits are in lots of vendors catalogs. The simplest source is ebay.
Keep in mind that the huge foam collar in the pivot post is just a filler where the body panels might not line up perfectly, they didn't need to. Any water that goes past that seal will go same place rain goes through the fresh air vent, into the cowl. The part of the wiper pivot seal kit that seals the cabin is the foam gasket and rope caulk collar at the pivot post mounting flange.
Another member kept finding water in his left fresh air vent and dripping out that interior door. Turns out a screw had been removed that held a window washer part in place. Water went directly into the vent box from that open screw hole.
