A good type of foam for ear/headband cushion replacement?

I have Sennheiser Momentum 2. They do not sell headband replacements (and they are finicky to remove/reassemble).

But the headband has decreased - especially the bottom side with extra thin "leather". The foam is completely flat.

It's all susceptible to skin oil damage.

But what kind of foam would be the best to use - considering it cannot be thick (under 1cm) and would somewhat resist degrading and going flat.

I may also use the same foam for ear cushion foam replacement on dt770 (that is sitting In the drawer as backup, but the foam is completely dead + buying new pads is just not worth it).

So having some good foam available at home for fixes would be great.

Possibly different types?

Also need to consider what is a good way to shape them (buying block/vs sheet for different uses?).