Sometimes, I wear striped knee socks with my UK's... They actually go pretty well with my survivals and my spartan... Another source is <http://www.sock-dreams.com>.

I've bought a lot of the socks I wear with my UK's from them. Their Military Boot Socks would go well with either a black or a green UK. The striped ones go well with pretty much any color UK. My traditionals usually get paired up with kilt hose.
-J