Audio Technica AT-1005II parts

A friend of mine recently got a fantastic deal on a technics sp-15 with a AT-1005 mkII tonearm. Overall the deck and tonearm are in fantastic working order. The only problem is that the tonearm is missing the counterweight. Being that obviously these are now long out of production, where the heck could I find a counterweight? Has anyone had any experience with where to find vintage parts or even possibly an after market counterweight?