DC voltage stepping down but keeping current uchanged with no regulator
I assume that when you say...


  keeping the current constant


...you mean keep the peak current capability of the reduced-voltage supply as it were before at 2A max.

Without a regulator (of the conventional type) you are probably stuck with using a zener diode and feed resistor. The regular 5 volts needs to drop to 4.7 volts so choose a zener diode of 4.7 volt rating. The current draw (before the zener stops operating at its knee point) is 2 A and this dictates the series resistor between 5V and zener: -

R = \$\dfrac{5V - 4.7V}{2A}\$ = 0.15 ohms with a dissipation of 0.6 watts (choose a 1 watt resistor).

The zener, on the lightest loads, will be consuming the most power and this will be Vz * 2A = 9.4 watts. Best choose something like a 12 watt or 15 watt device.

That's how to do it without a regulator and it's an ugly power hungry solution but will work.