AR Customers - Adding attachments or leveraging Customer Data Management?

Content

We would like to attach customer documents (such as contracts) to the overall customer versus an invoice, however within Receivables - Create Customer, there is no place to upload an attachment.

An alternative we were considering is putting these attachments on the actual organization (under Customer Data Management > Organization > Attachments). However, these attachments would still not be available to view in Receivables.

Additionally, I am thinking that uploading the attachment in Customer Data Management would have to be a secondary step after creating the customer in AR, because it does not seem possible to create a Buying Customer with an Account in Customer Data Management > Organization - It just seems to create the Organization and Site.