I actually found my old Tekna Sonic C-10s.
I don't have the additional magnetic pads that you would originally stick on to the speaker to hold them on, though. I used to put them on top of a speaker and seemed to hear a difference.
Looking for Tekna Sonic Vibration Absorbers
I am looking for a pair of the Teknasonic Vibration Absorber Model C-10. It’s that plastic gizmo (from the eighties or nineties?) that sticks onto the back of a speaker to reduce cabinet resonance. I’ve scoured eBay and other sources. Does anyone have any leads for me?