They are listed on Eurospares. The earlier parts had an integrated needle roller bearing. The later parts did not. If you wish to remanufacture them check the tolerances on the OEM part, as they aren't very tight. Race teams ended up manufacturing their own inserts with reduced tolerances.
Cheers Mate. Yeah the new upper challenge bush I have here has a 1/2 mm slop on it. Not sure if im going to use Delrin will be bit to harsh for the road, me thinks, play it safe and go the poly route. Cheers