Thunderstone

This small purple white stone emits a bright light and loud bang when shattered. As an action, you can throw this stone up to 20 feet, shattering it on impact. Make a ranged weapon attack with the stone, treating it as an improvised weapon. On a hit, each creature within a 15-foot radius of the target must make a DC 14 Constitution saving throw. On a failed save, a creature takes 1d4 force damage and is blinded and deafened for 1 minute. On a successful save, the creature takes half as much damage and isn't blinded or deafened. An affected creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.   Can be slung from a sling, increasing the range to 30/120 and applying its normal 1d4 bludgeoning damage plus the effects of the shattering of the stone.
The stone isn't magical, its shattering properties are natural, meaning it can be infused with magic just like a normal pebble.   Cost: 25gp. Weight: 0.1 lb