It is really quite easy to build a power supply unless they have some funky chip in there or something. Considering that you want it to charge the battery properly maybe it would be best to find out what kind of PS they are using.
otherwise the hard part is getting a fitting plug. the 7805 etc is real easy to do.
I dont think there is anything grand about the power supply, it is a bit high tech (switch mode), but that is only to save weight, space and heat.
Who said that they hooked their modem up with their PC power supply? - And that worked well. So yeah, either a 7805 or a wire coming out of the PC box.
Thanks for your help guys, but I've found a power supply at Nowire's Menlyn branch. There is no way I'll be able to build a power supply.
And chuckl, perhaps YOU should get a life instead of throwing around insults. I realise that I put it in the wrong forum, but there is really no need for you to act like such a "chop".