Suggestions Or Help Please: Best Way To Create Purchase Orders Of Zero Inventory Sold Goods By Vendor By Date Range by Alan Kroll

My business model has me selling most items with zero inventory on hand. On a weekly basis, I order sold items from my suppliers who deliver to me within two business days. I then fullfill and deliver to my customers locally on weekly routes. 

Can anyone here suggest an app that would allow me to generate Purchase Orders By Vendor? I need to generate P.O.'s that include All Sold and Unfulfilled Zero Inventory Items for Specific Date Ranges.

I deliver locally on my own trucks only and do not ship orders. I also do not sell on any other platforms than Shopify.

THANKS!!