The correct term is a delta insignia pin. The best plce to try would be online, I figure. Don't try Star Trek.com, as it is no longer kept up-to-date. Anywhere from eBay to Amazon to any of the other merchandise sites might have it, or something similiar. Specifically, the insignia you want is an operations insignia,which has a sort of swirl on it.
Keep in mind that the ones used in the film were probably not shiny metallic, usually insignia like that are resin cast to save money and have a matte finish so they don't reflect the studio lights. I searched around, a few sites had the larger metallic chest pins for the service uniform. StarTrek.com does have a "lapel pin set," but I don't know if those would be close to the ones used on screen.-Cpthunt (talk) 02:15, March 30, 2016 (UTC)