Well after a considerable amount of Googling, I have found my answer:

http://www.applefritter.com/node/10169#comment-44810

http://lowendmac.com/pb2/wallstreet-powerbook-g3-i.html

Okay, "almost" found my answer. I now know what will work. But alas, searching for that Kingston part number (KTA-PB100/256) only yields high density SO-DIMMs, not the low density versions shown on Sonny's photos. Any ideas on where I can buy these would be appreciated.