Are you looking for 4.8V or 6.0V?

If yu want 4.5, then go to radio shack and get a 5 volt regulator (about $2.00). The part is a 7805 ic regulator. It has 3 leads (in, ground, out) it will handle up to 1.5A.

If you looking for 6v then google 7805 regulators and you will find several ways to make it regulate 6v.

Larry