If you're are looking for the most authentic material for your restoration, you''ll need to get a hold of some leather from the Nile crocodile,
Crocodylus niloticus.
I know that for instance South Africa and Zimbabwe have commercial farming operations of this species, specifically for the leather and they export a lot of it, so the required papers should be routine to obtain. I'm sure it won't be difficult googling your way to a supplier either.
If you are satisfied with a visual similarity, I say go for your good ole' native American alligator,
Alligator mississipiensis. - Once skinned and minus the head, croc is croc, and nobody will be able to tell the difference.
Good luck with the project and please update the thread with photos, so we can see the awesome results!
All the best, - Thor