Dagnabbit, I has a ship-load of large knob info — can't find any of it.
One thing I do recall, was Mable Audio had a number of bigguns: http://www.mableaudio.com/en/products.asp?sid=12
44mm, 60mm (Jawn is about 60)... in that ballpark.
I've raided a few knAWbs off disposed Washing Machines/Dishwashers and Dryers...
And it's only $2.19!!! Woooooo!