I'd love to keep my 12L quiet when running in the neighborhood. Hyperdrive belt and pulley system did just that. Almost silent! Love that! Anyway, is Hyperdrive still in business? Can I buy the pulleys and belts still?

They're still in business but the drive belt and pulley stuff has been out of production for quite a long time. You might find some on ebay or other buy-n-sell sites now and then.