I see a number of those red filter caps on eBay so you could find a light that has an appropriate diameter bezel and away you go.
Or.. One of these brings me back to my childhood. Lol
http://www.ebay.com.au/itm/261679296798
I have a rigel starlite which has red and white led and variable brightness. Not a bad thing but needed the edges of the lens blacked out, would be better with a diffuser type lends to stop the eye a seeing the naked leds