I have about 8 of these cameras that have four piece fibre/paper bellows, joined at the four corner by 4 strips of "leather" (with black cloth underneath). This is really good system. The paper bellows last well and only 2 of my cameras have leather folded corner damage.
I have done some temporary repairs with tape which makes the compression thickness for the stowed camera difficult or impossible.
I have measured the thickness of the leather to under 0.5mm. This is not a thickness that is commercial available in the usual hides.
Rummaging around my female relatives dress making scraps has revealed that snakeskin is a possibility and I know that tanned fish skins have the right thickness and have used for telescopes.
Snakeskin has the advantage that it is the right length (65cm) and width "from the hand of nature". This may sound a bit overdone but the Continental cameras did have quite colourful leather edges.
Would be pleased to hear other opinions/experience of working with these materials, like giving it a fold and strength over time.
I have found a local source for both snakeskin and fishskin. Both are produced commercially and not on the CITES list.