My friend went through this a couple years ago with an aging pair of SM120s he owned. After looking into NOS (expensive!) and modern replacement options--of which there really weren't any great ones that would retain the efficiency the speaker is known for as well as other T/S parameters--he simply went ahead and refoamed. They came out at least as good as new and after cleaning the pots, sounded as first rate as an SM120 is capable of.
