The part number on the 65 Wildcat console shift switch is a 1371068. Buick parts books indicate this same switch was used on some, but not all 65-68 models. Cars using it were the 65-66 models with ST400 transm, 67-68 long console Wildcat and Riviera, 65-66 long console cars with ST300 transm, and the 65-66 LeSabre. As far as my resources indicate, no other GM brand used it.
This kind of part shows up sometimes in odd lots of stuff on ebay. Some old-time Buick dealers or AC-Delco parts places might have one. Though lifespan might be limited, there are probably some still left in junkyards.