Have you heard of www.ravelry.com? It's a website for knitters/crocheters that enables users to, among other things, keep track of their stash of yarns. You can search through users' stashes and find users who have discontinued yarns in their stashes and you can contact them to ask them is they'd like to sell the yarn. You'll have to become a member...it's free...but there are over 1 million members so your chance of finding the yarns you're looking for are pretty good. Good luck!