Old thread, but kid came today with an old Tony Hawk 20'' bike that needed a left hexagon crank arm, and a search led me here. Anyway, while I later found one currently on Ebay (RARE Hexagon/6 sided spindle Left Crank Arm, from St. John's, Newfoundland) for about $45, he had no $ to spend anyway, and I replaced it with a one piece crank from an old one-piece single speed, same size chainwheel and bearings, and it works fine, for free (except for new pedals at cost), thank God.

Tthanks for the info on this thread, and may it help certain others come come looking for obscurity.