Two other pad options are: Cobalt XR2 or XR3's, or Carbotech XP-10 or XP-8.
Disclaimer, I don't have a Rush (yet) but I do run a Lotus Exige which uses the same pad sizes so I know they are available. Cobalt and Carbotech are popular options in the Lotus community. I personally run Cobalt XR2's...