BU level security implmentation for Peoplesoft Inventory module

What is the delivered functionality to implement security for  PeopleSoft Inventory 9.2 module based on below requirements without implementing BU level security?

We have two Inventory business units, say A and B
PO, AP, GL Business units are same for both the inventory business units.
Inventory BU a  has its own inventory location and inventory BU   B has own inventory location 
purchasing Item master is same and shared by both the  inventory business units
Inventory items are configured for BU A and BU B separately

User Tom is  the user,  need only access to BU A - inventory items and order processing  and receiving / put away and replenishment