Adding a DC-to-DC converter to my LED light

[VioletSky]

While I wait for my CMG/Berger infinity ultra, I was thinking of adding a DC-to-DC converter to the LED light I now own.
It's a completely unremarkable 3-white-bluish-LED, 3-AA-cell light built by... I have no idea. It's got "LED-LITE" and "super-bright" stamped on the casing (but it isn't). There are no other indications of the people responsible for its existance. I bought it for Not Much at the local electronics store.
It's a very simple circuit... no converter, no regulator, just three AA cells in series, a resistance and 3 leds.
It's made like this (I forgot to take a picture of it, so I just opened the GIMP and quickly drew it. I am perfectly aware of the awfulness of the result, by the way):

(should the image not show, just copy-paste the link)

That black dot is the click-switch. It sits atop a square rubber protrusion that runs for the whole length of the battery compartment. Apart from the small section of it that contains the switch, the rest is just plain rubber. It'd be no big deal to hack a nice compartment in it with my dremel.
Now, the LEDs aren't driven at anything like their maximum capacity (either that or their maximum output really sucks)... I'm guessing this light has a monstrous battery life (I haven't used it enough to know for sure).
What I'm looking for is for some more light output from the light (driving the leds harder) and a way to regulate the voltage from the batteries, so that when they discharge or when I use NiCD cells the output doesn't sag.
Since I'm good at tinkering with stuff but know close to nothing about actual electronic circuits... what do I need to make myself a small DC-to-DC regulator that always spits out the same voltage no matter what input it gets?

 

[Lynx_Arc]

I would measure the current used on the light with new or fully charged batteries (if using rechargables) and possibly consider just changing the resistor at first. Nicad and nimh cells tend to *sag* in their useful operating life very near optimum voltage to direct drive (without circuits/resistors) lights so I would guess when the batteries hit their long flatline the resistor value is too high for that causing it to be dim. I have the same problem with a 3AAA light on nimh.

You rarely see regulating circuits on 4.5v reference lights because there is not enough headroom to justify a buck cicuit and a boost cicuit wouldn't work either until the voltage dropped down below about 3.5v or so on the light.
I would consider buying a uke4AA eled instead of putting a lot of effort into a inexpensive generic 5mm LED light.
I haven't seen any boost/buck circuits diagrams out there but I am sure there are probably a few of them and perhaps someone can point you towards one of them. You can buy circuit modules also but the cost would be 10-20.00, close to the price of the UKE4AA eled light which would end up being a far better light than what you already have there.