Autocomplete via API without reference

How would one create an auto-complete textbox that is able to search via an API and store one or more attributes from the API into your entity without having the search entity as a persistable entity in your domain? I.e. I store the values directly on the entity I’m busy editing. e.g. MyEntity has attribute MyAttribute that is a string value. As the user types I call an external API that searches for the value the user is looking for. On selection of an item returned via the API I store that value in MyEntity.MyAttribute. The key here is that there is no association to another object (the lookup data) because the data exists in a 3rd party system. The auto-complete textbox on the marketplace requires that you select a reference to the search entity. But in my case I don’t have that. I was toying with the idea of a non-persistable entity, but that does not work with the auto-complete textbox due to the owner of the assocation when it comes to non-persistable entities. The auto-complete does have an “on change” microflow where one could probably trigger storing the value where you want it to be, but you cannot get away from selecting a source (the association to the search entity). 
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