When the conversions were popular for the first style Nismo, guys were cutting pieces from black plastic trash cans for the protectors. Shape wise you can get pretty close using pictures. I did a thread a while back someone asked about these. I'll see if I can find , mght help.
This will give you a good idea of the shapes, the attach only to the bumper and use plastic rivets, if you can find the rivets elsewhere do it because they are roughly $4+ a pece and you need like 12 of them. It's towards the end of the thread you will see the pics of the protectors.
Requesting pics of Nismo front fender lining