Drawer glide back bracket replacement

I have no part numbers of the guides on my 21inch drawer. It seems the broken rear bracket, that I need, is attached to a single-track in the center bottom of the drawer. Everything else of the parts and hardware are working well. The center glide slides between two plastic slits /with a set screw to hold it tight. See photos. Hardware was install in 1992. (HK-14 written on the back)