Can't answer your questions off the top of my head. I am pretty sure though that the proof must have been known to the ancients. There could not possibly be any copyright restrictions.

In the proof #35 there's a link to a fellow who sells a 5 pieces puzzle that goes with the proof. His product may not be very suitable for 3-4 graders as the pieces have sharp edges. However, it is remarkable that even such a simple puzzle is not altogether trivial to solve. I'd be utterly surprised if anybody discovered the Pythagorean theorem using that puzzle.

Proof #9 may be a different matter. Indeed, all you need is 4 equal right angled triangles. First arrange the triangles as to make a square hole as in the first of the diagrams in the proof and make the students trace the outer square. Then rearrange they triangles as in the second diagram.