I recently had my E-body Rallye instrument/gauge cluster worked on. There are 2 screws that mount the Speedo to the back of the cluster housing. The screws use a unique style "hat-shaped" washer and rubber anti-vibration isolator bushing. I believe deterioration of the rubber bushing is a fairly common problem (as can be seen in the last photo). I imagine these isolators were commonly used in other MoPar makes/models. What have others done to remedy this issue? I don't believe these are easy to find, or even if they're available anywhere. I need to replace both of the isolators. Thanks.

The company that worked on your speedo head should have them.
If not I can look thru some of my stuff. PM me thorough the board and reference this post to help remember.