For many years the only jacket-waistcoat combo I had was a Highland Green Combo from the Celtic Croft. Although it's listed as premium, it is not a 'name brand' tweed. Their selection is limited, but the price for the two-piece set was good and they've seen much good service; I've worn them to casual weddings, informal opera performances and other such like. If you want more variety, as others will no doubt go on to suggest, try either USA Kilts or the STM. And by all means, keep your eyes peeled on sites like Ebay (as long as you're not my size ).
Blake