This instructable makes one from parts you can find very easily and cheaply.
Step 1: Supplies
1. LED flashlight, the one i used is from a walgreens, you can get these lights for much less on ebay, about 99 cents.
2. Red Photography Gel, This was free from a photo store down the street they give away sample packs to students.
Step 2: Take Apart Your Flashlight
Step 3: Cut The Gel
Step 5: Results
This flashlight will be very useful on your next camping trip!