I have parts that are used across customers so I'm looking for a single report that shows all of my item shortages and includes the job or PO

There's an Assembly Shortage by Item report in QuickBooks Enterprise, tlatham. 

The report also a column for On PO. Here's how to look for the report:

1. Go to the Reports menu, look for Inventory.
2. Select the Assembly Shortage by Item.
3. Make sure the From and To dates are correct. 

There's also a Shortage Report by Vendor which has the same column for On PO.  You can also refer to these articles in case you want to customized, memorized, or export the report:

• Create, access and modify memorized reports 
• Customize reports in QuickBooks Desktop 
• Export reports as Excel workbooks in QuickBooks Desktop 

Let me know if you need anything else when running an inventory report.