I know there is at least one shop, but I don't remember if they have much of a selection? Is there others? (we have been to Scarby one weekend the last 4 years)
Kilts are a lot like a suit. You can buy an off the rack suit or you can buy a custom tailored suit. If your just looking for a "kilt like garment" a good kilt like a good suit is hand made and it's a great investment.
The Scot Shop is at Scarborough. They are owned by another company who operates at least two booths under different names at TRF. What they have is not bad for Faire wear. They will also do special orders.
Scot Shoppe (http://www.kommandokilts.com/)
I have to vouch for the Scot Shoppe. Their customer service is above and beyond. I accidentally ordered an incorrectly-sized shirt off their website, but didn't have time to have another one shipped before my trip to TRF. I didn't want to buy-and-wear at the festival because I wanted to wash the shirt before I wore it. They offered to have the shirt set aside, already washed and air-dried, ready for me to exchange when I got there.
As mentioned, their kilts are off-the-rack, and I think they're all standard sized with a 24" drop. However, their selection is bigger than say, Stillwater Kilts.