If you have access to 240V mains, then get this power supply from the Dick:-
http://dicksmith.com.au/product/Q175...y-13-8v-dc-23a
I have used one of these for a few years and it can drive quite a lot of gear.
1) keep it out of the rain and heavy dew (just cover it with plastic)
2) disable the green light in the switch and even replace the green LED with a red LED - they light up the observing field!!