For what it's worth, this one looks interesting to me:
I wouldn't spend much more than $4.
Excuse me for barging in the topic once more; if you were just looking for a cheap dc-dc converter; there are plenty of ready-made circuits being sold on the internet with free shipping. Take a look at this: http://www.dealextreme.com/p/8.....ubec-45214
(dx is pretty bad, but alas) . Search for "dc converter 5v" on ebay and tick on "free shipping" (the hrd converter is a very popular design, though a bit bulky). It makes absolutely NO sense to pay $3.41 , $6.89 or even $15 for a single component, which might need several additional components and a circuit board to put them all on. (components are really expensive when bought as a single unit).
DeliciousRaspberryCake (now you're making me hungry... ), you're completely right. I was browsing around for some pre-made conversion circuits, and it seems like I'll want to use them instead of engineering my own solution on a PCB. A UBEC seems like the perfect device: it's cheap, efficient, and replaceable. I was looking at this one on Pololu (pretty much the same thing as the DX link but it looks better made):