Joe,
I was lucky to find this one in a local gun shop here in CA about 2 years ago for only $ 50...but as Ron posted, prices on these have been going up.
I have helped one or two other Members find some on eBay and other sites as well through relentless surfing...they are out there...but may take some time.
I have seen 2-3 poor conditioned ones in my travels to gun shows as well, but too worn for my interests.
Here is one of my Mauser-Interarms rigs :
