How Do I Add Vendor Item Code to the Line Items of a PDF Print of Purchase Orders?

The Vendor Item Code field is available on Transaction Searches, and is displayed on the PO form web page. However, I cannot find a way to add to the printed PDF form for a PO. The ID is {item.vendorcode} on the Transaction Search. I created a custom transaction column field with this formula, but it displays as "ERROR: Field not found".

Obviously, when you send a PO to your vendor, it is highly desirable to include the Vendors Item Code on your PO. The Inventory Item record allows you to add Vendors, and their Item Code for the Item.