The Associated front B3/B4 rims and the Associated B3 rear rims will work - these will let you mount the newer 2.2" tires on the car. Make sure you get the B3 wheels as the B4 wheels have a different offset that will not clear the travel-links on the trailing-arm suspension on the JRX2. If your cars do not have the trailing-arm suspension then either of the Associated or Losi rear rims should work.
I have one as well that I keep for nostalgia reasons and was able to update the tires for the rare times that I want to take it to the track. XX, or XXX front rims will not work since they put all the wheel bearings in the hub - you need to have a front rim that allows for bearings to be installed in the rim (like the Associated stuff). Duratrax buggies also has rims that may work and are a little less expensive.