How to setup Item cross reference for new entity

Summary:

How to setup Item cross reference for new entity

Content (required):

We have a new entity (XXL) being onboarded to Fusion applications. They are willing to align their item numbers with the rest of the business entities from Canada but due to nature of business they want to retain their old item numbers somewhere. It is not just documents that they would require to display these old part numbers but also within the system for all the various functions they perform within Oracle listed below.

For example, if they perform a PO enquiry, they would want to see their old part number within Oracle along with the new item number