Check out these from Altronics:-
http://www.altronics.com.au/index.as...item&id=M8627A
http://www.altronics.com.au/index.as...=item&id=M8990
Re inverters, modified square wave will generally be ok for plugging a laptop power supply brick into assuming your laptop is the sort that has a external power supply. If its the sort that have internal power supply then pure sine wave may be better but modified square wave may not give any problems.