Related Item functionality for Phase Out product

When my company replaces existing items with new items, there are two options - Setting up a supersession in Item Relationships or Setting an item to a Phase Out status where they can still order the original item if there is availability.  The problem is there is no quick way to check the availability of both the Phase Out item and the item that is replacing it.

Is there a way to use a tool like the Related Items in OM, which will show both the existing item and the replacement item's availability in the default warehouse and then the option to pick either one from that tool?  I tried setting the item related to itself in hopes you could see both lines and their availability, but that is not allowed.