I dig where you're coming from. The closest thing that I've found to a "plain" looking kilt jacket is the Wallace Jacket at Scottishkilts.net. I understand the desire for all the "trimmings" that some guys have but I prefer a plainer style...sort of the contemporary look. That's what's needed is that Navy Blazer cut to kilt length...something that you can wear to work or to a less than fully formal function.
Unfortunately, all you can do is have a regular jacket cut down or get one custom made...makes me miss the traveling Hong Kong tailor that used to come to town once a year to take orders.

Best

AA