I've just bought an RCDynamics booster.
They aren't made 'en mass' from what I gather but are supposed to be more reliable than almost anything else.
Elliot Harper used one in the IFMAR 1/12 worlds A Final
Input Voltage 2.5-5.8V
Output Voltage 6.0V
Quiescent (No load) Current 3mA
Typical Efficiency 90%
Maximum Current 1.5A
Maximum PCB Size 15×20mm
Maximum Size including heatshrink 17×23mm
Weight Approx 6g
Input Wire * 130mm 22AWG Aircraft Spec
Output Wire * 90mm 26AWG Aircraft Spec
Connector JST/Futaba Style