repairing old Koss ostrich-egg headphones

[douglas baldwin]

I have a set of those big green Koss headphones, got 'em for $5 at a yard sale. The current model is Pro 4AAT, but these are old (probably Pro4AA) and revive fond memories of of my first sound-on-sound experiences and listening to Forever Changes and Revolver. You know the deal.

So in the process of trying to find an intermittent short in one side, I open up the ostrich egg, only to find that the foam insulation in the shell has completely disintegrated into some dusty/sticky industrial waste. I'd like to repack thit with something that won't cause a mess in thirty years (assuming we still use two ears, or even have two ears in thirty years). Any suggestions? I'm thinking cotton.
dB