Why not replace it with what was on your tandem. Many parts are available on E-bay as New Old Stock (NOS). Used stuff also has a lot of life left as well. THe gearing on you bike, if it truely is a 99, appears to have been modified as 10 speeds were not available in 1999, it was 9 speed era so you or someone already has done some modifications if you have 10 speed rear/chain.

As far as I know, you could use a 9 speed triple FD such as a Dura Ace FD-7703, rated for 53/39/30, or Ultegra FD-6503, rated for 52/42/30 but should work for a 53T large chainring. You could even try a 10 speed triple Ultegra FD-6603, rated for 52/39/30.