After trying a few things to reduce or eliminate vibrations, I felt the best way would be to slightly lift the drip tray from the surface it was sitting on. This both creates a tighter fit against the main unit so the drip tray itself has zero play, but also acts as a dampener on the countertop itself. Bonus points for it having a little more grip. Found printing it at 3.5mm height was the perfect tension on the tray, but you may need to give it more height if yours is more worn or warped at all.
I printed this in TPU with 15% infill on a textured plate and used waterproof glue to hold them in place. They fit pretty snug and have worked great over the past few weeks.
The author marked this model as their own original creation.