You could make one yourself. Or maybe you could find something on ebay.
If power and heat are no issue, then there are some simple linear constant current sources.
Making your own switchmode current source from discrete components is a bit more complex, but do-able.
If you've looked at the LED guide I pointed you to, one of the first things you would have seen is the voltage vs current curve for LEDs. The key thing to note is that a small change in voltage can produce a massive change in current and that the process is such that it can run away with the result of killing the LED in fairly short order.
The key thing is the current. If you place a resistor in series with the LED, it will drop a greater voltage and the LED current increases, partially of offsetting the runaway problem. You choose a resistor to set the LED current, but in practice you need to know some voltages to do that.
Constant current sources are the best way of driving LEDs and they become "more better" as the power dissipated in the LED increases. Switchmode current sources have an additional benefit that they don't dissipate large amounts of heat themselves.