The Liberator derringer[1] which caused such a fuss a few months ago only needed a nail, which wouldn't be detected under most circumstances. I imagine that using an epoxy pin would probably be suitable given the gun's other single-fire characteristics.
[1] It's single shot, uses a low-powered cartridge, and is a bitch to reload; calling it a handgun is an extreme stretch.
[1] It's single shot, uses a low-powered cartridge, and is a bitch to reload; calling it a handgun is an extreme stretch.