Entronik via Amazon offers Prime members the Aduro AquaSound Waterproof Bluetooth Shower Speaker
in Black, Blue, or Pink, model no. WSP20, for $16.99
with free shipping
. (Non-members can spend $35 or more to qualify for free shipping; otherwise, shipping costs $5.25.) That's the lowest total price we could find by $6. It's compatible with most Bluetooth devices and features a built-in microphone.