Wifi Repeater/booster - 5 Volt low power, detachable antenna??

[#1]

I do a fair bit of camping, as a Scout leader, with family, with freinds and so on. a good few sites/places have no phone signal but wifi can be found, however the wifi is usualy incredibly weak

 Due to the nature of the beast, there is no access to mains power, or even 12 volts, however I have plenty of usb power packs of varying capacitys

So the question is, is there a wifi repeater that can be powered from a USB powerbank ( 5 volt) that has detacahable antennas?

 It will be packed into a bag/rucksack, so fixed antennas wont last, built in antennas wontn be as powerful ( i intend to also get a  reverse sma antenna that could be mounted in a tree/on a pole/whereever for increased coverage )

 It also needs to be easy to set up, preerably using a phone with the minimum of fuss.

[#2]

@pint 

i doubt you'll find one. Probably your best bet is to get a Huawei E5577 Mifi unit. From reading the manual you can set these up as a Wireless Access Point  or in other words a wireless repeater instead of using their normal mobile data feature. The feature is built in to enable it to be connected to a WiFi hotspot when one is available.

These have their own battery and are charged from a USB charger. They are about the size of a mobile phone. They have internal antennae plus connectors to enable an external high gain one to be easily fitted (and removed). 

[#3]

@pint 

Further to my post yesterday I have since got my brain in gear. The external antennae function on the E5577 is for improving mobile data reception, not WiFi. Consequently the local WiFi range will probably be limited to range similar to a normal WiFi extender. I have one so if you are interested in this solution just ask and I will do a comparison for you.

Sorry for the duff info.