If it's just the vintage dolls you're after, I'd suggest finding a proxy for places like Yahoo Japan Auctions and Rakuten auctions (though Yahoo is generally the most active in terms of active auctions up at a time), and checking out Mandarake's Doll category daily. Fair warning though, they are obscenely priced most of the time no matter where you find them.
If it's just the headmold and face you're after though, I believe that Club67 and/or Licca Castle make reproductions. They're somewhat cheaper, but I don't see them on the second hand market very often either.
Good luck in your search though! I know I'd love to have some of the vintage Licca dolls myself, especially Rie-chan (one can dream) but for now I'm just sticking to the newer releases ^__^