It's just as well or better to run a little bead of Permatex Blue RTV Silicone Gasket Maker around the base of each prong. The plug housing in the linked picture can be disassembled. Damping the plug from inside the housing with Permatex will accomplish more potential benefit, providing a greater amount of sonically neutral vibration damping. (The plug receptacle in the wall can be damped sparingly, also.)
As far as a product suggestion for a grungebuster gasket, this idea has been kicked around off-and-on for several years now. Some customers have made gaskets with thin grungebuster material, with mixed results. Others have used grungebuster Dots to fit inside the prongs along with washers that fit around the outside of the prongs, again with mixed results. Plugs come in different shapes and sizes, and having a die-cut product to fit most or all plugs might not be practical considering a probable small demand and iffy results. Herbie's grungebuster material is best suited as a decoupling interface and plugs must couple in order to work.
I think there's a product to be invented though, and the idea is surely worth exploring further.
Steve
Herbie's Audio Lab
