Right after I bought my 1991 three years ago, I bought a boat load of new and used spares, just in case. Found a 28 amp alternator from a 5000 mile wreck which I added to my spares stash. Over the last 2 1/2 years, I have seen NO serviceable spares at local wrecking yards; all are leakers or overheated from high mile bikes. All those I have seen on Ebay have no credible history associated with them, have burned or broken wiring, or obviously leak oil from the harness exit......not safe bets given the amount of labor involved in replacement.....and asking prices are all in the ridiculous range. Unless you really make a lucky find, the upgrade to 40 amps is the best alternative.