I know GunitPaintball.Com
has parts kits for Mavericks, but I'm not sure if they're the same as Trracers. Bulldog Paintball and Airsoldier also have some olde skool parts, but not for Trracers from what I can see.
Like dukie said, the only ways I can think of to adjust velocity without the screw are with a nelson spring kit or by using a regulator. I used to use a CMI R2000 between my quick change/3.5 oz tank and the ASA.