As an update, you will find excellent, exact dimension perfect grilles on ebay with “sculpted-foam-innovations“ on ebay. He is the only one making the correct thing dimensionally, color wise, etc.
I talked to him for some time on the phone. His commitment to the L100 is
beyond serious. He owns many and knows everything about them. His
dimensions are taken from the original grilles he got from someone in the JBL
parts dept. some time ago.
The creation of these grilles requires a large investment in time and money. He
related to me the process- hot wire cutting on an NC machine with massive
ventilation for that and the colors applied.
One thing I learned was that the badges on the grilles were originally both on the
left lower corner. In the late 70's they started making them left and right lower
corners
See my post concerning this here:
http://www.audioaficionado.org/jbl-a...storation.html