Additional commercial models are avail for $20-$99 and up. Some of these put out 5-10 watts of light from LED's!
Custom models have over 10,000 Lux of output with 3v-6v batteries in series with fully regulated power supplies! But these are expensive...
MY Instructable uses FREE sample LED's and original base & components, fully reversible and backwards compatible!
see those other expensive mods at http://www.flashlightreviews.com/mods/mods_index.htm
Step 1: LED convert without use of Bulb base & solder...
Bend the LED (10mm) as shown and set it in lamp base holder...
Use longer lead for (+) positive center tip contact.
Use shorter (-) leads for negative side or flange contacts...
Spacing or contacts vary by light and model. Keep LED contacts springy and coiled to absorb shocks and bumps.
Step 2: Mag-Lite LED conversion (any 2xCell Flashlight)
Many types and even flashing models avail. Easy to swap, 3mm LED's can be stored in butt caps of C/D Maglights.
Retains original lamp capability. Just slide led leads trimmed to 1" into pins for lamp....easy
Cheaper than off the shelf conversions or upgrades!
Higher quality Nichia, SuperLux or Powerful Cree 1W LEDs available.
Sub $1 LEDs do not have same power.
Voltage regulated IC controllers can be used for longer battery life. Easier is to swipe a Everyready Emergency cell 2xAA charger. This is a easy 3v-9v regulated LDO or Buck Puck. ideal for C/D cell Mag-lights.
Step 3: Bulb & Filament types
Long shelf life, low power & unbreakable.
Any AA/C/D flashlight can be converted to LED with any bulb and intact retrofitting back to original.
Step 4: Assemble
LED Power varies, use high quality 3-4v Ultra Bright LED's and observe voltage recommendations. RED LED's are often 1.5-1.7 volts and 2x AA batteries will burn or shorten LED driven past limits.
0.5 watt Nicha and Luxon LED's are avail in small packages.
I added a Cree Xlamp 7090 XR-E series See below...