There's nothing special about them, they're just regular Scotchbrite pads. Green SB, as NJStroker said, is around 600-grit, and it's available just about everywhere. Try the aisle in Walmart with the dish soap, dish sponges, and such. The blue pads are there, too.
I've found the maroon and grey pads at the local paint store, a couple of bucks for a 6x9 pad that you can cut into six 3x2 pads.
SH