Check out Zareason - the prices are pretty reasonable. I like buying from them because they've vetted every part of the hardware to make sure that any distro you want will work on it, and they'll find you the packages to install if the weird one you chose doesn't have them.

I actually do the reverse - buy a Zareason and install Windows on it for freelance projects that I need Windows to maintain, because I know that after the maintenance window has ended on those, I can throw Debian on it without issues.