Thank you, thank you, THANK YOU to everyone who offered suggestions about where to find Dr. Pepper in Santiago! Just as Lydia said, the Jumbo at the intersection of Grecia and Macul (Jose Pedro Alessandri) had a stash. As you can see below, they also had A&W root beer.
Unfortunately, I have very little self control when it comes to things that are delicious, so all this was gone within 24 hours of me purchasing it.
This just goes to show how useful our little gringas-in-Chile blogging community can be when it comes to information exchange!
Oh, and I haven't forgotten about Part 2 of my "Why I Came to Chile" story. It's on it's way!