The sporran and matching belt were a gift from my darlin' wife Maggie. She found the company, Centaur Design, on the web. She called them up and spoke with them, they then looked up the colors of the tartan, and then they custom dyed both pieces to more appropriately match the colors in the tartan.
I'd say that that is pretty good service.
As an aside, their shop is located at Traquair House, http://www.traquair.co.uk/ ,the oldest continually inhabited home in Scotland.