This might be something thats small but your hoping you don't lose. Measuring just 3.75 inches square and only 1.5 inches thick, the Bose Soundlink Micro Speaker ($110) produces surprisingly booming sound for such a small speaker. The secret is in the custom-designed transducer, dual-passive radiators, and battery that were designed in tandem as a single system. As a result, this tiny speaker can provide up to 6 hours of clear, satisfying audio per charge. It's waterproof, the silicone exterior holds up well against bumps, falls, dirt, and sand, and a durable strap makes it easy to attach to whatever's around. Did I mention you could use Siri and Google Assistant as well with this device. Available in black, midnight blue, and orange, it can also pair with a second unit for full stereo sound.