When I researched this part I found that it is part of the boot, which I could not find either as new. Your best bet is find an assembly on ebay. I would like to find an extra retainer as well for a spare.

Here is one: https://www.ebay.com/itm/2004-2008-C...ss!45238!US!-1

What makes them more rare, it that when you buy an aftermarket shifter, you must reuse the retainer from the OEM.

James