Delighted to hear again from you, @Todd Miller.
The Customer Type can be manually added as custom field on the sales form. Let me walk you through in doing so.
First, let's add the custom field in your sales form.
Once completed, you can now add Customer Type on the sales form.
For a more detailed information, you may check out these articles for references:
Fill me in if you have other questions about tracking your income transactions. I'm just a few clicks away.