These speakers have a rubberized casing making them very durable.
Brad's Deals Editor Michael,
This iHome iBT12SC Rechargeable Flask-Shaped Bluetooth Stereo Speaker drops from $39.99 to $17.49 with free shipping at NeweggFlash. This is the best price we found for one by $6. This speaker measure 3.94" x 4.57", so they're roughly the same size as a real flask. They have built-in mics, an eight-hour battery life, and an aux input for a wired connection. There is no sales tax (except CA, IN, NJ, and TN).