Even if you are able to put a white LED into it you might find the batteries don't have enough current and high enough voltage to properly run a white LED. Red LEDS typically require less voltage and current than white LEDs.
I've only found one so far, that I gave to my brother in law.
Its the TekTite KnifeLite. A review can be found here. The knife part LOCKS which is really really nice and is flat tipped to work as a screwdriver. The white LED is very bright (for a 5mm) and significantly brighter than any Squeezie type light Ive found. Plus it actually is a true white, instead of blueish.
However, it uses 2 dinky batteries so it wont have very good runtime. You would only use this for very short intervals when walking from your car to house or whatever. If you want a more usable light, then get a keychain AAA one which is MUCH brighter and much better runtime, plus easy battery change. Then you can get a small gadget-knife that will do other stuff too.
I have a SwissTech KeyKnife that looks like a key, but you can open it up into a knife, dinky saw, dinky screwdriver. Your choice of gadgets may vary.