To request an Invoice from me that Combines Shipping, Please use the Cart feature in eBay to add items until you are done. Then hit the "Request Total from Seller" button. If you don't do it this way eBay will force you to make immediate payments for each item you buy and you will be charged excess postage in many cases.
Here is a You Tube Video on how to ask for eBay invoice:
https://www.youtube.com/watch?