Dick Blick is a great source for art supplies. They carry just about everything that you could need, an consistently offer the best (lowest) prices available. When I was doing price comparison for linoleum block DB beat even the local art store's prices, inlcuding shipping.
Right now they are having a clearance sale and I thought I would bring to attention one item. Showcase Portfolios are very nice carry and storage cases, and are usually $47.95-67.95. They are on sale now for 75% off = $11.99-16.99.