You may not find an exact replacemenmt for a 16 year old shifter,but upgraded replacements are WIDELY available,from budget conscious units to high end. I agree about taking it to a shop if possible (or at least giving pics and info on what exactly is on there),to make sure compatibility isn't an issue...but it wouldn't be overly expensive to upgrade the complete transmission to modern bits at someplace like nashbar.com,or pricepoint.com if you have any kind of budget. Or you could always singlespeed it out using your derailluer as a chain tensioner