I replaced a bad wiper motor and now need to link the transmission arm (not wiper arm) to the motor, but it appears that no one including dealerships have this bushing/connector. Does one exist? Can it be substituted with something else?

 

When we get a situation like this where specific parts just are not available we have 2 choices.
1. Replace the entire wiper transmission linkage , part is dealer item.
2 Maybe a salvage yard , but if it is worn as yours was, not worth the trouble.

 

Crazy there's no sources for a wiper transmission bushing available from a dealership or aftermarket supplier.
There must not be too much of a demand for it........or buick doesn't want you to pay 3 or $4 for a bushing, but rather a transmission and a motor at 3 or $400.