I take it you’re referring do Poppers as in the west coast dance style? One style people wear is a khaki work shirt with khaki slacks (but I wear straight Chinos and because it’s all I could find but look just as good). The shoes that are popular are called Hush Puppies and there is no specific head ware. Another outfit especially liked by boogalooers is a waistcoat over a shirt with dressy trousers Hush Puppies again and a long blazer. I’ve seen people wear dressy hats as well. But honastly the beast thing you can wear is what you prefer. These are just styles that have been popular.