Those are the old 15mm Ral Partha wolfriders, right?
I had something of the opposite problem - three wolves surviving from my misspent youth, but no riders. But I accidentally acquired some of
these riders (sans mounts) in an eBay job lot, and they fit perfectly. So I suspect the RP goblins would work fine on the dragons.
I can check tonight and see whether the
15mm.co.uk wolfriders fit on the RP wolves. From memory, I think they did, but the dragon riders looked more imposing. I suspect the Ral Partha goblins are small enough to go with those wolves (which are nicer miniatures than they look "raw", I think):

I think the
15mm.co.uk boars would probably work well - or better - too.