In War of the Twins book 3 chapter 11, Raistlin gets the device/pendant from Gnimsh just before he kills him.
In chapter 13 Tasslehoff already has the magical device again:
“But, now”—the kender glanced around—“the first thing to do is find Caramon and tell him I’ve got the magical device and we can go home.
I couldn’t find in the book how he gets it back. Did he steal from Raistlin during his their conversation in the cell? It seems strange that Raistlin didn’t disassemble/destroy the device again knowing that the device was the cause of the explosion of the Portal in Zhaman.