I beat you to the punch. Yesterday, after reading this post (but not the part about dropping trousers) I went to the Salvation Army store and found a really nice tweed jacket which I'm going to hace cut down to wear with my kilt. It's a "Deansgate" brand, from S & K Menswear. I got it for $5.
It doesn't really match my modern Lockhart, but there's a light blue stripte in it which will perfectly complement my Carolina (when I get it).