well, you could use any random charger or power source you have lying around that is ~7-8 volts, but you need 3.3v as well, right, and last time I checked you were pretty sketchy on wiring the regulator, so, you might want to be safe and just rewire the original power plug for the original power source and use that. However, if you are feeling crafty, then yes, you could use an old charger or something like that to power it that doesn't necessarily have to be the large brick of an n64 power source.
*whispers* get that multimeter