If it is a standard K98 mount/endcap assembly, any company that sells Mauser parts on the internet should have, or know where to get, one.
I believe, however, those parts are serial numbered to the original gun.
How about some pictures of your friend's gun?
"The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza
Baby Jesus cries when the fat redneck doesn't have military-grade firepower.