Power Key Design for Variable Voltage Power Supply
You can try a device similar to the TLP190B that is an optocoupler device but its output its a photo-voltaic device that can be used to drive a MOSFET. You might just have find one that will suit your switching time requirements and output characteristic that can still give you low power consumption from the If of the optocoupler diode and enough Vout to drive a logic level MOSFET.

Additionally if the isolation is not required you can just do the swithcing with a suitable logic level MOSFET. 

Another option is to use a relay and some external circuitry to drive the relay hard for a short amount of time and then just drive it with enough current to keep the contact closed

And finally a suitable latching relay could be another option