All you need is 4.5-5 yards of double-width (56"-60") wool tartan fabric, and you have a "great kilt." You might be able to find it in a local fabric store. If not, talk to John at Keltoi (one of the sponsored vendors here, and located in Ontario) and he can order you the cloth from any one of the usual Scottish mills.

For a truly authentic plaid, as previously mentioned, order 9 yards of single-width (28") tartan, cut it in half, and sew the two pieces together along the long edges. Your final product will be 4.5 yards long, and now double-width - and just like the plaids of old...!