A 3" by 3" by 1" rectangular chunk of electrum with two copper nodes protruding from one side. A glistening of blue sparkles come from the electrum caused by a powdered blue dragon scale added into the silver-gold alloy.

Attached to any metallic weapon in a way that the copper nodes touch a metallic part of the weapon. 

Once per short rest after hitting an attack you can activate the Zap-a-Tron to do an extra 1d6 lightning damage to the target, however the wieldier of the weapon also takes the extra lightning damage. A kink that could possibly be worked out with more field testing. 

Notes: Damage: Lightning, Damage, Combat, evocation