Ball bearings (bag of 1,000) in D&D 5e costs 1 gp, weighs 2 lb..
As an action, you can spill these tiny metal balls from their pouch to cover a level, square area that is 10 feet on a side.
A creature moving across the covered area must succeed on a DC 10 Dexterity saving throw or fall prone.
A creature moving through the area at half speed doesn't need to make the save.