Efficient low-power buck (step-down) regulator IC for Li-Ion - 3.3V conversion?
You don't want a switcher. Your input-output difference is so low (for most of the discharge curve the voltage is less than 3.8 V) that even at 90 % efficiency it won't do better much than an LDO.

Have a look at the Seiko S1167:  


Ground current typical 9 &micro;A  
Available in 100 mV steps from 1.5 V to 5.5 V   
1 % output voltage accuracy  
150 mA output current  
150 mV drop-out at 100 mA  
Shutdown input  
SOT23-5 package


edit
Found an even better one in the S1313:  


Ground current 0.9 &micro;A  
200 mA output current  


Seiko doesn't give data for ground current under load, but in my experience you should count on 1 % of load current, so at 1 mA that would be around 10 &micro;A, most likely less than 50 &micro;A.