Levy's MSSC8U-008 Hummingbird 2 inch Cotton Guitar Strap
The natural cotton of these straps is more comfortable than many other nylon straps of a similar price. Do one for the environment and get cotton instead of artificial fibers.
Two inches wide with a sliding resizer, this strap will size from 53 inches down to 27 inches. This style of strap (with a sliding adjustment) is what we will generally recommend for children due to the range of sizing.