This item was manufactured by PRIER for a short time during 1983 and 1984. Unfortunately, most parts are not available.
The packing kit used for this hydrant is the same as the current packing kit, part # C-134KT-803.
The seat washer for this item was a 1/4L beveled bibb washer, secured by a #8-32 x 3/8" bibb screw. This type of replacement bibb washer is available from any plumbing wholesaler or hardware store.