I totally agree with Knitette, my origins are from the granite city, Edinburgh but I now live in North Wales. The Celtic knot I have always believed to be more of Irish and Welsh inorigin but have not found a truly Scottish based design as their claim to fame is their beloved Kilts, although they seem to favour the wholecloth method
http://books.google.co.uk/books?id=B...origin&f=false for quilts.
I have made a number of quilts for my Brother in Scotland and he loved all of them but the only one that had a truly Scottish touch was one that I backed with a lovely piece of wool which had a miniature plaid design on it, similar to the Stuart tartan. I think this link
https://www.google.com/search?hl=en&...cp.r_qf.&cad=b gives some of the best suggestions IMO. Do let us know how you get on pretty please.
Ooh did a quick search for you and found these on EBay
http://www.ebay.com/bhp/cotton-tartan-fabric