I had to get something a little more "Renny" when we performed at the Renaissance Faires... and the Minnetonka High boots were perfect! In fact, I saw a LOAD of the regulars in them. They not only look great with any kilt (plain, tartan) but they're comfortable as h_ll.
Another thing that a person could do is what the Black Watch and other Scottish Regiments did in the French & Indian War: wear wool leggings under their kilts -- the leggings, usually in blue, red or green, was something they picked up from the French and Native Americans -- Stuart Reid's Osprey book "18th Century Highlanders" show a Scot in this variant, wearing traditional mocassins.

You can see a picture of the leggings here:

http://www.eagle.ca/~harry/vehicles/worth/queens.htm

Cheers,

T.