Hope it's not too late for a reply. As a owner of three RC36 ProClasses I totally understand your desire to ride the fork again Best idea: Contact Josh or Adrian at Pace Cycles, they still host a fine stock of spare parts for the older forks. You can reach the guys at +44-1751-477737. Just explain to them which part you need and it'll be on its way! Cheers!!!
I did get in touch with Pace a while ago and those springs where not parts they still held in stock, but I will get in touch again. The forks work fine at 70mm of travel, it would just be nice to bump that up to a more useful 90mm.