If it is a ball, I would at least do the eton jacket conversion with a tailor. An Argyle type jacket will likely look underdressed. A proper Prince Charlie would still be the best. Check out local Scottish shops near you, a lot of them will rent the jacket and waistcoat for a decent fee. There are also a lot fo shops that do online rentals. Cheaper than buying one, especially if you don't think it will get a lot of use after this event.