Ebay is probably your best way to go, simply because it will probably be difficult to find one anywhere else.
A couple of comments: if you're sure you want to retain your '87 electrics, make sure the harness you are looking at shows only 1987 in its fitment chart. I just saw one listed as fitting 1987 through 2008. There's no telling what you would get there, because '87 through '08 covers at least three different harnesses.
My recommendation would be to get the harness that fits 2002(ish; don't remember exactly if '01 is the same) to present and get a side cover, stator, flywheel and new CDI to match. It will probably cost around $500 total for the parts. That's what I did to my '87 because I want it to be around for the long haul and parts availability for the newer ones is much better.