From the products page you can also request a bulk redelivery for all customers who owns a specific product.
Click on the truck icon at the right side of the desired product.
Then click on the "Mass redelivery" tab on the top.
You may then provide an optional message to be send along with the redelivery.
And then you can click on the "Mass Redeliver" to start redelivering this product to all customers who owns it!