Bikebandit.com seems to have good prices and you get a 10% discount if you have an AMA membership. Free shipping for purchases over $100, I think. Ordered an OEM petcock on Sunday, sent from CA, received in OH on Friday, for $72 shipped.
But, I have found you need to shop around to find the best price on any individual part, especially taking into consideration, available discounts and shipping vs. free shipping.