Most of voltage regulators should work as current regulators ..
For example the LM7805.
Tie a resistor between the output terminal and the "gnd" terminal.
Choose the resistor for whatever current you want (Iout = 5V/R + Ib, Ib is around 3mA, check data sheet of the LM regulator; Iout should be <1A).
Then connect a load between the "gnd" terminal of the regulator and your real gnd (DC RTN).
The main issue is that you will lose 5V across the resistor, as it is 5V regulator ..
If you consider 12V regulator you will lose 12V, etc.
The LM317 has the reference voltage of 1.25V and that is the reason it is much better choice than other regulators, 5V, 9V 12V etc. ..
:wink:
IanP