You can upgrade to 9 speeds by replacing the index gear and may want to replace the front ratchet (EC-RE133; my formerly 8 speed shifter with the original front ratchet would only go from the 4th to 2nd largest instead of three cogs bigger to the largest on a 9 speed cassette before I bent the lever outwards a bit). Officially you're also supposed to use the thinner 9 speed jockey wheels and pulley bolts.

Good luck finding one and note that you need a 2000 and older 9 speed gear EC-RE113 which uses the same derailleur pull ratio as 8 speed instead of 2001 and newer one which matches 10 speed geometry. You could try Vecchio's Bicicletteria in Boulder, CO.

The down-side to doing that and sticking with first generation ergo levers is that the right G-spring carriers (which break) have been discontinued (I haven't checked to see if a newer one fits well enough after you cut-off the clock spring post) along with thumb lever return springs (my current one seems to be holding up, but I've had them go soft on the right side and replaced them when I had the levers apart for the G-springs).

G-springs (currently EC-RE209 on the right side) are the same as with second generation levers and should remain available.