Sandtrooper and Probe Droid
This is a fairly simple custom to dress up the Sandtrooper that came with the 3D Cantina Playset. Just take the backback from a regular Sandtrooper and cut a hole in the side (shown below) where the clear rod of the probe droid will fit.
Close-up of hole for Probe Droid
Next, cut off the slot part of the clear rod where it fits into the sandtrooper's back. Before gluing the rod into the hole, I recommend you put the backpack on the trooper, either by cutting holes or gluing it on (I glued it on). Lastly, test the probe droid's placement by putting the rod in the hole. Adjust the length of the rod as necessary, and glue in place when done.
Now, I'd love it if someone could tell me why the 3D Cantina Playset didn't come with Wuher in the first place. That's almost as ridiculous as packing Wedge with the Carry-Case Falcon.