Organization Relationship for Guest Users

Summary: How do I create a relationship between a guest user incident to an existing organization without making the user a contact for that organization?

We have user that may belong to organizations that we have but they are not contacts. We want to have a custom field on the incidents table that allows us to record an organization against.

I have tried https://community.oracle.com/customerconnect/discussion/comment/261101#Comment_261101 and linked incidents and orgs. But the problem is that the custom field will display with no_value (typical for contact with no org) and the field is read only.