Violent engine shake? It'* not the coupler. No way in hell. When couplers go bad they cause a rattling sound at idle, but no shake. The coupler and supercharger are incapable of creating engine shake. ABSOLUTELY incapable.
Remove your SC belt. Spin the SC. Does it spin ok? Yes? I knew that was your answer. Look elsewhere. We need you to pull codes, and give us all the details on your typical tune-up items, and their ages.
Even if it were the coupler, buying one from a 'blown' supercharger would be like combing the wrecker for used wiper blades. A new coupler is less than $30 and this is a 'normal wear' part. It'* that way by design.
You really need to look elsewhere for the problem. In fact, I'm so confident and bold, I'll gaurantee you this:
If it'* the coupler, and you mail me your old one, I'll buy your new coupler from ZZP.
In other words, it isn't.