Rob Roy, though not appropriate will do. Though there are "kilt police" who might object, the polite ones will say nothing. The formal sporran, if you purchase it is not appropriate for day wear. Ditto on the kilt police.

If you know "the rules" and explain that either one is your first purchase and youknow the rules, I have yet to meet anyone who strenuously objects.

Yes, I am a kilt police, but I also understand that two rules of etiquitte apply:

1) You know the rules and would apply them if you could, or
2) You do not know the rules and they need to be explained in a polite, informative manner.

In either case, no gentleman or lady should give you a hassle, beyond making sure you know the rules.