Finally I managed to buy a RPi 0. To supply RPi 0 I use a small power bank (Blow 4000mAh). Additionally I added a power switch and micro usb port for battery charging. To be able to use standard usb WiFi card you will need a small adapter (micro usb to usb). I closed all the electronics in a black plastic housing with dimensions: 124 x 71 x 38 mm. Because I wanted to be able to easily disconnecting the camera from the robot I've used strong velcro to attach the camera housing to the robot.