Hi sticky-monkeyflower,
If the items you wish to combine use the same checkout system, you will be able to send your buyer a combined invoice using the "Send Invoice" option on your My eBay page. As soon as you click "Send Invoice" next to one of the items, you will see the option to combine them on the ensuing page.
If you are using Auctiva Checkout and your buyer selects insurance while completing the combined checkout process, a combined insurance policy will be automatically generated to cover these items upong checkout.
If you are not using Auctiva Checkout, or your buyer paid for each of these items individually, you will have to contact our support department for assistance with purchasing a combined shipping insurance policy.
-Mike