You can start with that Internet Auction Site. Your local fabric store might surprise you. Many Highland Outfitters will sell you yard goods, including several X Marks sponsors. Poke around and see. Probably you will need to decide what kind of fiber you want ( wool, poly viscose, acrylic) what weight, and, of course, which tartan to start with. I expect you may find that you won't save a lot of money, but you will get a better fit and better construction if you do it yourself.