Looking for recommendations to control a 12V alarm flashlight


I have my Arduino based alarm sytem and found a 12v 500mA alarm-flashlight which I would like to use.

Now I have 2 problems here: 1) where do I get the 12 V 500mA from? Battery with step-up? Need a 12 v charger? 2) how do I control this flashlight? Relay?

Can anybodysteer me into a direction? Idealy with a ready-to-buy solution from some vendor, because I am more the programmer guy and not the solder-iron-savy guy..

Any hints are appreciated.

Here you are.
Can use any NMOS TO220 transistor with drain-source voltage greater than 30 volts.
No need of heatsink.
Supply voltage can be from ac/dc adapter or a battery with charger.