Parts listed here are designed for both the HK UMP and USC carbine models chambered in 9mm, .45 ACP or .40 S&W unless otherwise noted. MGW offers replacement triggers, sights, magazines, firing pins, screws, springs and other small parts for these rifles. Outfit your Heckler & Koch UMP or USC...
www.midwestgunworks.com
Here’s a good start for you. Not sure exactly what you need but midwestgunworks always has a good selection of oem parts for the brands they carry.