It was a one off independent shop in Vancouver that I found from phoning around. I was very specific about the thickness I needed and what they had was extremely close. I think their stock in trade was more yarn than fabric.
FWIW, I was taking direction from skywavebe. After finding the right felt, I agonized a bit over how to cut the perfect size, perfect circle then put a precisely sized hole dead center. Lee suggested hollow punches punches of which I bought a set but they were too dull or I didn't a big enough hammer so they wouldn't cut Jack Squat. I tracked down someone who did visual presentation who happened to have a laser cutter. Was going to go that route but then Sam let loose that it could be done freehand with a pair of scissors.