Through KLOV forum I read about the "Magic Eraser", a product from Procter & Gamble that turns out to simply be a piece of melamine as produced by BASF.
There was also a link to a Korean e-bay seller offering these "same" sponges for quite a good price (about 13 euro for 60 pieces INCLUDING shipping).
I ordered a box and they arrived very quickly.
Since I didn't want to risk any of my precious machines, I tried some of them on Erik's Gravitar which happened to be the closest machine around

Seriously, there is no (or VERY little) risk with these things, collectors have been using them a lot from what I read....
Well here are the results:


