Controlling 50+ RGB LEDS using Arduino

When you get up to 3A , the MOSFETs will be a better way to go.
Where are you located?
I usually use digikey's search filter to find one.
What you want is:

  • N-channel mosfet
  • in stock
  • logic level
  • thru hole
    then sort by cost
    browse the resulting list, getting past the 1000 and 2000 qty prices, looking for Low Rds (down in the 10's of milliohms) and low Gate Capacitance (for fast switching) with the needed power handling and package style that's comfortable to work with.

For example:

If you can't order from digikey where you are, then look for those kinds of parameters in the parts from the source you can order from.
It needs to be Logic Level so the MOSFET turns on full with 4.5-5V. Otherwise, you will need some buffering in front of the MOSFET, the output of that buffer will need to able to go to 10-12V to turn a Standard MOSFET full on.