USB Foot Switch FS1-P , primarily manufactured by PCsensor (RDingtech)
HIDMacros (by HIDMacros.net) or LuaMacros (the newer version).Warning: The "official" driver from many Chinese OEMs is often unsigned, triggers Windows Defender, and only works on Windows 7/8. It is notoriously buggy. usb foot switch fs1p driver download better