I had got some droppers usually used in medical treatment of eyes, nose etc.
One of them was big enough to house three AAA batteries.
So I used a 1w or 3w led and turned it into a torch. Yet powerful and easy to keep in car for emergency purposes
Step 1: Size
Place a AAA battery and note the size. Bottle should be a few mm higher so that a small aluminum piece can be attached to led. The reflector would be attached outside.
Step 2: Cutting Bottle
After measuring at appropriate position cut it
Step 3: Reflector
Small key ring torches are available I used its reflector. Cut it from below than sand it(Be careful scratches can appear inside if done roughly). So that led can enter it
Step 4: LED and Switch
take the led and wire it. Solder it in after confirming its working as you want. Take a button and attach wires. A two step button can provide 2 power options HIGH/LOW
Step 5: Ending
Check it and complete by some finishing of rough edges. You can cover the front by some transparent plastic sheet.