Howdy, Perfessor!
Annie has mentioned a couple vendors. How authentic do you want to be? My wife is from Scotland, and I've looked into getting a whole outfit. Ya got a spare 3 grand or so layin' around? That stuff is EXPENSIVE! There's the Kilt, which (as shown in the movie Braveheart) is wool and wraps around the waist and up over the shoulder. I seem to remember that with the proper pleats and folds and such, it's about 7 yards of premium Scottish wool! Yeah, they make 'em now that are more like skirts, but still, there's lotsa wool in those "authentic" Kilts. And what is authentic now really hasn't changed much in the centuries. There's the Sporran, socks, shoes, pins and clips, shirt, Skihn Dubh [pronounced skeen doo, and there are various customs about that - the sock knife, or most correct - black knife] and a host of other little details. If a Soldier, a Dirk and Claymore (basket Hilt version) would also be proper. There's WAY more than I know or have time to type about. There are some fascinating facts associated with the full outfit, as each piece has its own history. And I don't want to be a party pooper, but a woman in a kilt and cowboy boots wouldn't be very authentic - BUT! There are modern women's kilts, and since I'm not the Grand Poohbah Authenticity Expert on Scottish Women's Fashions in History ... well, Miz Annie can get all the style points she wants with her Kilt and boots!
I wish I could refer you to some really authentic sites - the prices will make you run out and buy a couple Colt pistols to save money! If you want, PM me and I'll call and discuss it over the phone, 'cause even with my limited knowledge, I could probably talk for an hour or type a whole day!
Miz Annie, I humbly do hope that you DON'T take what I wrote as a personal insult! Just trying to explain the difference between Scottish authentic and Americanized clothes.