I suspect you will be able to find something similar in the hardware section of a brake parts catalog. If not...get a flat washer with right OD, drill to right ID, snip out a section and work it into there!
I can't really see your picture that well, and I'm not familiar with column shifters, but if it is a "C" clip (or other type of retaining ring,) you might want to try McMaster-Carr. They've got everything! http://www.mcmaster.com/#c-clips/=7nxqf5