How can we control the default Source of the items on Requisitions creation from Catalog?

Content

Our business case is as follows: 
1. We have an Item (Item A) which is associated to multiple inventory organizations on the same Business Unit. 
2. The Central Warehouse buys the Item A externally from Supplier and also with a Blanket Purchase Agreement. The rest of organizations sources/replenishes on hand from the Central Warehouse 
3. Item is enabled for Internal Transfers in associated organizations. But the attribute for Source is different. Item Attribute on Central Warehouse is set to Supplier; while on other Inv Orgs it is Sourced from Organization. 

Steps: 
1. Procurement > Requisition 
2. From the search page or catalog, search for the Item