You can of course just purchase cool looking cowboy hats (some options are below) or if you want to go all out, bedazzle them too! I like to add short song titles, a band name or an easy band logo.
If you aren't quite committed to the cowboy hats, how about some glasses? Or go in true fangirl spirit and do both.
Etsy has some of the best options for personalising accessories to match your pre-planned outfit or even t-shirts to get the exact vibe you want.
Maybe started by Taylor Swift but it doesn't have to stop there, making friendship bracelets is easy, quite relaxing and makes a great addition to an outfit too.