Stock item is out of stock

Hey everyone,

How would I handle a situation like the following:

• Item A is a stock item at company XYZ
• Buyer from XYZ tries to order item but it's out of stock (both direct and through distribution)
• Item A lies in two IC81 par locations

Which would the buyer do:

1. Order a substitute item as a non-stock and then just deliver the item as normal
2. Order a substitute as a non-stock and transfer that stock into Item A even though it's technically not the same item
3. Other 

Someone brought this up to me earlier today and I wasn't sure what to do.