First of all, practically no one you'll be mingling with even knows what a semi-dress or formal sporran is, let alone care that you're not wearing one.

I personally don't own a "formal" sporran. I just don't like fur. I have two plain day sporrans (brown and black) and a black semi-formal with a silver cantle, which I wear when I'm dressed to the nines. However, unless it's a somewhat formal occasion, I'll wear my day sporrans with an Argyll jacket (black with the black Argyll, and black or brown with the charcoal jacket, depending on what shoes I'm wearing). I think this looks just fine, and like I said there aren't too many kilt police around to tell me I'm doing it "wrong." Besides, most kilt police like to go undercover and wear trousers, so who are they to tell me what I'm doing wrong?

Andrew.