IRF450 that was also suggested has a lower on resistance (0.4 ohm ) but the datasheet shows a TO3 case which will probably not be convenient to use.
There are many models that could be used but IRF740 (TO220 case) would work fine for your application and can handle more current and voltage that your specification, It is cheap and you should be able to find it easily.
The power consumption on the mosfet will be about 5W with 3A load, If you find it high then there are mosfets with lower on resistance but probably more expensive and I don't know which ones will be available in your area.
Alex