A cheaper way to get a set is to find a second hand 2000 model onwards that is sitting in a dealer with them fitted and offer an exchange of your non adjustable units plus a given dollar value. Early Bergs had them fitted standard, particulary the FC models.
Even though the 2000 on had 43mm, the tops of the forks are the same as the 48's. I have swapped the caps from a 00 FC501 to an 04 FE550.