I basically made a workaround by co-opting the "ship via" list.  Our business does not require it, so I use that as a list of our repeating/seasonal online sales.  I then added it to the templates I need it for (sales receipts for the online purchases and a custom Invoice I created for offline purchases of the online sales) and changed the title of the field in the formatting.  

This has worked perfectly for the time being.