Make a frame like a painter would use for their canvas.
the 700 level insulation from Owens Corning would work - 703 is the most used.
A price alternative that works just as well is Johnson Mainville - look for the rigid fiber board products on line. Their prices are a lot lower and made from the same stuff.
Wrap it with fabric. You can get any type of fabric, but the main point is to keep the fibers from making it into the air and getting into your lungs.
Any fabric store would do. An online specialty store is Gilford of Maine. http://www.natfire.com/products.html
that fabric is fire retardant.
"ROCK ME! Roll me through the night!"
If you can find some office cubicle baffles, they work great. I have my rehearsal space lined with them. They suck up an unbelieveable amount of sound. I got em all free from a company that was vacating a building.
Look into Knauf Duct Liner - it was about 1/2 the cost of the Owens Corning 703 when I bought it and has a better absorption coefficient. Like Cram suggested - wrap the frame with GoM acoustically transparent material.