when i need random odds and ends, i post a "Wanted" ad on Craigslist in the bike section.

when i buy parts i also usually ask if they have anything else and make a mental note of who seems to have lots of random parts in case i ever need something

you can convert shimano shifters with a band to downtube shifters with a "Shimano DownTube Shifter Boss Adaptor"

heres a set of shifters on ebay at 99 cents right now: http://cgi.ebay.com/Shimano-Down-Tub...item2c5cc667ad