if your customers have an account - they have access to ALL of their orders within their account. They can click on any of the individual items within an order and it will take them to the product page for a reorder at the current pricing of the item.
Each email notification to a customer upon order submittal also provides a link to their order page with in their account and they will find the same listing of products and can click on any product and it will take them to the product page.
Is this not adequate for your customers? Perhaps you could add some information to your site about these features?