http://www.drumfactorydirect.com/index.php?main_page=index&cPath=14_92_102_172
Fish skins. My SanXian is python skin (more than 50 years old and so far no holes) and that makes me think of all the alien pythons in Florida that need to be removed from the habitat. Fish skin seems like a good match to cat - deer skins (which are given away at hunting slaughter houses where hunters take deer to be turned into sausage) are another possibility, but likely too thick.
I cannot believe that sturgeon are non-threatened in the Nile river, but I can find no data on this population. Birdlife International does operate in Egypt, and the Egyptian Ministry of Environment puts out high-minded goals and papers but not action. Regardless, fishskin might be a good way to go - buy a whole salmon and work from there. In Japan, fish skin glue is a go to for shoji paper fastening.
Considering the tone of the shamisen it is tempting to think of making a National guitar-style shamisen with a shiny nickel-silver top.
The tropical hardwoods that are used to make shamisen are of more concern to me than the skins. Sustainable and harvest are two words that really do not go together - as a naturalist, I have done surveys of single oaks and found dozens of species living in one tree. That number goes up hugely when looking at rainforest trees. Every tree that falls is a whole universe to the creatures living there.
Buy old shamisen and rehabilitate them. It is the most responsible thing one can do, I think.
Celluloid (and the resultant cascade of plastic in the world) was created to replace ivory - to make cheap balls for pool tables. In the end it did not help elephants and now we have oceans capped with floating plastic that is beginning to degrade to a foam of plastic (interesting news there is that new ecosystems are already emerging that make use of the plastic, from naturally occurring bacteria that digest long chain polymers to fish that lay eggs in the debris, the bad news is still the bad news - dead albatross, etc etc). Mylar was the miracle that replaced skin for drum heads, playable in all weather. Mix in Kevlar and you have a material that you can beat on and breaks down to asbestos-like fibers of kevlar in the landfills.
Then again, here I am typing on a machine whose manufacture has left one of the most toxic pools of black sludge/heavy metals in China:
https://www.google.com/maps/place/40°37’32.9"N+109°40’10.1"E/@40.6433994,109.6801445,6460m/data=!3m1!1e3!4m2!3m1!1s0x0:0x0
Turns of that to make pretty and shiny you must separate out the ugly and awful.