I bring you - the parametric traffic wand generator! Use your own flash light of choise.
 

Parameters:

OuterLightDiameter = The measured outer diameter of your flashlight
TrafficWandDepth = The depth of the shroud-part that should extend downward
TrafficWandLength = how long the traffic wand should extend from the base
TrafficWandEndHoleDiameter = End hole diameter, reccomend 50% of the outer light diameter 

Suggesting printing in PETG, ABS or ASA etc.
Please bare in mind that PLA might not be the best idea for this, especially if you keep it in your car and it gets hot, not to mention if the light produces heat that can start to soften the PLA.