Cherry MX Rubber O-Ring Switch Dampeners (125pcs) - Keyboard Accessories - Products
You can get them there, but they won't help too much with the blackwidow. They'll muffle the noise from bottoming out but the Blue switches are clicky/loud by nature of the switch. If you think you'll have an issue with the noise the blackwidow stealth sold on the razer site, or a different board with browns/reds/blacks would be a better bet.