How can I restrict Data access with respect to supplier and supplier site

Summary: How to establish restriction based on supplier and supplier site. We have a business scenario where in business wants the data to be shared only with specific external buyers having required BU, Supplier, Supplier site combination access provisioned?

Ask: Below is the example where in External Buyer is provisioned access of procurement agent access for PROC BU1. Now the expected outcome required is to control the access based on supplier site that is Site 1.

Sample Mapping structure required
Supplier	Business Unit	Supplier Site	Site Assignment
ABC	Proc BU1	Site1	Req BU 1
			Req BU 2
		Site2	Req BU 3

And similarly, even the manage order search should also be refined by supplier site 1 access.