Reply to Headphone driver sources

I've used the Technics RP-DH1200 cans for quite a few years and what I do is to take them apart the minute I open the box, sell off the headband and cables because all I want are the cups and drivers inside. I use only one side, you see.

Anyway, I'm currently down to a few empty cups and only one working driver. There was this evil DJM-400 which seemed to like blowing Technics RP DH1200 drivers because that was all it ever spoilt. 3 of them!!!

Now I'm wondering whether anyone knows of good 50mm drivers which I can try. Doesn't necessarily have to be Technics drivers if they sound good.