Need to store Site Location address for Customer that are not Default Billing or Default Shipping

Hello!

I have researched this issue all afternoon with no success.

I need a solution for storing a Site Address on transaction documents that are not related to the Customer on the document. Currently, staff are using custom field that stores free-form text, but as you can guess, inconsistency with entering makes this almost useless for reporting/historical purposes.

For example, I enter SO for customer, but I need to assign a Site Location where the items will be installed for the customer (Customer may have mulitple site locations--think customer owning different.Convenient Stores/Gas Stations).

I thought about custom record; however, the same Site Location needs to be used on Purchase Orders as well as Sales Orders and Quotes and Returns and Cases.