You can get these Aduro Smartphone Sport Armbands for $7.99 on Groupon. Shipping adds $2.99 which makes your total $1o.98. There are two types available that will hopefully fit the phone you have:
- Armband for Apple iPhone 4, 4S, 5, and iPod touch
- Armband for Samsung Galaxy S III, Galaxy Nexus, HTC One X, Droid Razr Maxx, and other Android devices
These sell for $14.99 on Amazon.