Lanyards, they are the easiest thing to use to display pins in the parks. I have 3 that I wear, not always at once but sometimes.
BTW, you should visit the eBay super thread (link in my sig) about eBay and pins, unfortunately many sellers on eBay are selling scrappers. We have a thread here that can be used to learn more about eBay and scrappers. Enjoy your pin trading!!