New Take off
dot com sells complete leather sets for 04-08 screws that are original ford parts. $350 for the set, in black only.
http://www.newtakeoff.com/f150_leath..._crew_kit.aspx
If you want a different color or for a different cab style, try ebay or Katzkins directly. Katzkins can make you a set in multiple colors, custom piping, embroidery, etc. but they can run you upwards of 8 bills. I got lucky and found mine (supercab set in plain black)on ebay for $550 about 2 years ago.
Here is an ebay listing for a supercrew set, the seller is someone who has a good rep around here, others have bought from him and have been happy. I believe they are made by katzkin.
http://cgi.ebay.com/ebaymotors/Ford-...Q5fAccessories
If you buy a set and try to tackle the job yourself give this thread a read
The Official Leather Install Guide w/pics
and watch this video
http://www.motorz.tv/play/katzkin_le...r_installation