I'll bet if you call Krieghoff in Ottsville, they will send you a replacement for free. They did that for me when I had a problem with the front sight. I lost a center bead on a Beretta and Benelli and it can be hard to find replacments when they are metric threads. Good Luck.
I'd call krieghoff also. I lost the screw that holds the wheel on my adjustable rib. They sent me a new one no charge they also threw in a Allan wrench for my adjustable trigger. Again no charge no shipping & handling no processing fees nothing just asked for my address and said they'd get them sent out that day. Very pleasant people to talk to. Great customer service.