Efficient alternative to a charge pump for stepping up a 3V supply to 3.3V?
Google, or do a parametric search for,  "Synchronous Boost Regulator" and you will find many parts. For example, the TPS61020 claims 96% efficiency, though probably not under your operating conditions. 

Boost regulator because that what you need. 

Synchronous because you need synchronous rectification to get high efficiency with relatively low output voltage compared to a diode drop.