Hi Nick,
If you are in Canberra there's a few of us here that ride and race VMX. In fact one of us, TwistAndShout here on the forum, owned an 84 CR250 for a while a few years back. He *may* still have the workshop manual for it. I think he said he still has a few bits. Maybe PM him? If I remember I'll ask him about it tomorrow. Or PM me for his contact details.
Graeme