If you are willing to settle for the front sight, Brownells stocks a SP101 tritium front sight.
#957-121-101 SP101 Night Sight $60.00
If you must have rear inserts, check IWI or Trijicon; they offer installation services.
I don't have Trijicon's address on hand. Perhaps another TFLer will have it handy.
[This message has been edited by Daniel Watters (edited March 17, 1999).]