Looking for the name of a tech device from ANH

In the original Star Wars, there is a scene where Luke comes into the room where he was cleaning the droids and they aren’t there. He pulls out a cylinderical object, presses a button, and C3PO jumps up from hiding.

Does anyone know what that prop is called?
Droid caller, droid finder, droid remote?

I believe Han Solo had one on his tool belt as well.

Google searches keep turning up “how to locate your android phone”.

SilverWook said:

It’s a droid caller all right. 😃
http://www.partsofsw.com/lukdcanh.htm
http://www.partsofsw.com/handcanh.htm

Thank you SilverWook, I knew someone, somewhere would have one.