John,
If you can find them, buy them! The prices are going through the roof, even for the used ones. I don't imagine that they'll come back down again, at least not to last year's prices.
TheSamba is a good start, also ShopTalkForum, and the random 914 forums as well. Everyone who frequents these sites already knows the situation however, so the deals might be over.
I can ask some drag racing buddies to keep a look out as well. Of course, once you get a set, you're married to them. They aren't all that easy to rebuild/maintain/tune/etc. it took FOREVER so get ours set up and running right on the 1914 and we ended up going to a turbo in the end after all of that.
Luck,
TC