If you send the buyer a paypal invoice for the additional postage you will be able to add in the buyers new address and leave in the notes why the money is being requested and the ebay item # and transaction ID if required can also be noted in the payment request.

When they pay and you resend the item you can add the tracking number to the transaction on the paypal site and you will definitely be covered by paypal for seller protection as they will refer to the new tracking information.

You can also add the 2nd tracking number to the ebay transaction in most cases but there may be a time limit on that.