I managed to do it. Here's how (a couple friendly polizei assisted with my questions - it is awkward talking to a couple people sporting automatic weapons):

Go through security, follow the signs to the K gate area. Board the tram. After leaving the tram and going up, follow the signs for the connection to "L". You do not need to enter the terminal. You just go up the escalator one more level to "L" after you exit the long up escalator that dumps you in front of the terminal entrance. Follow that up one floor, to passport control. Go through, you are there.

The store In question for me (Steiff) was shut down and empty. Go figure. Neither the website, info booth, or polizei knew this.

To get back, follow the signs to go to "L", board the tram in the non-Schengen side to gates G, H or wherever you are going.