If you're strapped, something like this:
http://cgi.ebay.com/South-Bend-Atlas-Lo ... dZViewItem
If you keep watching and putting snipe bids at $11, you'll get one eventually. Also watch ebay for 3-jaw chucks. I got a Bison with 2-piece jaws and backing plate from a surplus place on ebay for $75 on buy it now. If you're in a hurry, Enco is about the cheapest for Bison.
Jeff at Tools4Cheap (
http://www.tools4cheap.net/) carries lots of used and import tooling. His Chinese 3-jaws are $120. They're not Bucks or Bisons, but they're on the better end of the spectrum for Chinese stuff. His QC toolposts are a pretty good deal, I have two of them. You can use a worn-out 3-jaw, which might cost $50 on ebay, you just have to complete your turning in one setup because you'll never get the work in the same place again.
For a 4-jaw, I'd look to the future and get one with 2-piece jaws which makes it a better candidate for a good set of pipe making jaws like my friend Mark Yingling made for me. (
http://public.jwh.fastmail.fm/images/Bison1.jpg) You can even use a 4-jaw exclusively and dial the work in like a machinist. Someone posted a picture here a while back of a Oneway chuck mounted on a piece of pipe held by a 3-jaw. It initially struck me as having more overhang than I'd want, but I've got to say it's a good job of making do with what's at hand.
Oneways aren't that much less than a machinist's 4-jaw, but you will see them on ebay occasionally, this category is good to watch for that kind of thing.
http://home.listings.ebay.com/Power-Too ... ngItemList
Hope that's not too much stuff at once.