MiniInTheBox offers the Milanese Metal Loop Bracelet for Apple Watch in Silver for $5.99 with free shipping. That's $9 under the lowest price we could find for a similar watch strap. It features woven stainless steel mesh and magnetic closure.
Note: This item ships from China and may take two to five weeks to arrive. Uncheck "Add Shipping Insurance to your order" during checkout to remove the 49-cent fee.