As far as I know, the following stores do not carry their own version of Dr Pepper even though they offer store-brand soda. They may carry other off-brands, such as Dr. Best or Dr Shasta, but their own line of soft drinks does not include a Dr Pepper derivative.
In addition, there are no Doctors in the lines sold by A-Treat, Ritz, or Jolly Good.
For the benefit of the firms named here, and any others wishing to cash in on this growing phenomenon, I offer my own list of potential names. Besides the obvious ones (Dr Y, e.g.), consider these:
Text and presentation copyright Dave Schul (dave@roadmaps.org), 1997-2003. "Wouldn't you like to be a Pepper too?" is a trademark of Dr Pepper/Seven Up, Inc.
Last updated July 27, 2008, when ALDI and Faygo were removed from the list.