A lot of places also offer tartan bow ties, that with the cumberbund should look pretty sharp. And perhaps a small Clan Crest badge or pin on the lapel.

But, why buy a tux? Do you actually go to that many formal events a year? At least with a kilt, you can wear the kilt with a polo shirt or sweater for casual things, not likely to wear dress pants when hitting the pub for a pint.

All things considered, good luck & Best Wishes!