Well, first off I'd post in the 'Trading' forum, you never know, someone on here might have them.
Otherwise all I can suggest is ebay I'm afraid. I'm pretty sure there were some character sheets up last time I searched for Heroquest (Friday I think), I think there was a card set too, but they may have gone. Just keep checking, that's my advice.
"Well it's Forty-one Thousand Nine Hundred Sixty-nine OK -
Gotta war across the Milky Way - "
Iggius Popiscus and the Stoogii, "41,969"