I was thinking a cool souvenir for US cities would be to get an FBI Challenge Coin whenever I'm in a city with an FBI Field Office or Resident Agency. Unfortunately, it is not clear to me how this might be done.
I got a challenge coin from the Austin Resident Agency from a friend who attended an FBI Citizens Academy and, according to him, he was able to get me one because, during one of the classes, they were selling FBI paraphernalia, some of which included challenge coins. That's not something I'm going to be able to do while on vacation. Honestly, it's not even clear to me how I'd get one from my own hometown, which has a Resident Agency, let alone from another city.
I'm sure I could buy the challenge coins on eBay but imho that cheapens the experience. I'd rather my souvenirs have a story behind them. Like "I went there and I got this" instead of "I went on eBay and I got this".