As long as you have a PWM or AC signal you might be able to use an audio transformer to trade your voltage for current. A 5-1 winding ratio would divide your voltage by 5 and multiply your current by 5.
Since you are just talking high and low you could also do it with transistors and a separate 1V supply.
Also remember that because something like a buffer amp has very high input impedance you can use a simple resistor voltage divider to attenuate the input as much as you need.