I'm not sure where to post this but... has anyone built a led flashlight? If so where would did you get the parts from and could you post some pictures. Thanks

Check out the instructables site.
There's a bunch of plans there.

https://www.instructables.com/howto/flashlight/

What is your skill level?  More specifically, with a soldering iron, using a DMM and understanding basic electronic principals?

I've only tinkered and it doesn't look that daunting to me, as you've got the host (tail cap/switch, head/reflector, tube), the star (LED mounting board) and driver board (electronics/guts).

Richard at Mountain Electronics stocks the parts and some hosts:

here...

CandlePowerForum.com and BudgetLightForum.com are two places with tutorials.

Chris

I get the whole do it because I can thing. Just not sure if it is cost effective.

Much like reloading, you get to tinker with flashlights quite a bit and you can really make a difference in the qualities of a given light, unlike much of the AR15 parts people buy and slap on, which are generally cosmetic in nature.

What I've learned after 6 years of readings lots of modding threads, is that you better be good with a soldering iron.  If you start getting the shakes, slam a beer quickly, 'cause you're about to muck something up, if you don't.

Chris

At roughly a buck apiece, 120 volt LED bulbs are a good source for cheap, bright white LEDs.

The typical design has around half a dozen of them, connected in series to a switching DC power supply.



The normal operating voltage is around 4 volts per LED, so a single LED is nice and bright when powered by three 1.5 volt batteries connected in series.

Or, bypass all but 3 of the LEDs, remove the DC power supply, and connect the remaining 3-LED-string directly to the bulb socket base. Viola - Instant 12 volt DC light bulb!

2032 lithium battery between a 5mm led's leads, instant light!