Like Darren, I make my own 7 string sets, but I order from juststrings.com, and every order has always been prompt. Occasionally something isn't in, so they ship what they have, but usually (always) they ship the missing string(s) to me after only a few days.
I use D'Addario XLS Stainless Steel Jazz .013-.056 (wound g), add a .070, and replace the two plain steel treble strings with D'Addario Electroplated .010 and .013 for the high e and b (these seem to last longer than conventional tin-dipped plain steels, and come in a nifty 5-pack). I tune down a whole step, drop C, and my B is at F.
I also use Elixir LTHB .010-.052, and add an Elixir .068. These also sound and feel great.