I am not sure where to look for it, but I have an idea and want to make a working prototype.
The first thing I need is some kind of curved composite backing material. it needs to be about 3’ X 3’. If you compare the curve to a clock, it would begin about 9:30-10:00 and end at about 1:30-2:00. This link shows something similar around a microphone.
It doens’t have to be expensive, sound absorbing stuff, just something functional to start off. The highest priority is that is must be curved, not angular. Even if I can find something at a Home Depot or something lke that, but I have no idea where to start looking.