I have +5v from a laptop and wished to get -5v for dual supplies.
Have found and ordered a volts converter 7660 which is just an 8 pin device and only needs
2 external C's to work. It can deliver -5v at 20 m/a with only a 1/2 v drop.
Haven't yet tried it but it seems an easy and cheap way to get a low current dual supply.
It can also voltage double and they can also be cascaded too.
Here's the spec..........http://www.ti.com/lit/ds/scas794/scas794.pdf