5v power supplies are easily available, Meanwell is a popular & reputable brand. The same psu can run your lights and microcontroller.
I recall the last time I wanted to do this, my problem with it was that my microcontroller had a different voltage requirement than the LEDs and I tried to put together a little circuit that delivered the right voltage to the microcontroller and LED matrix from a single 5V power supply. I think it worked kind of ok and then not anymore and I had trouble figuring out where I went wrong, most likely did some bad soldering somewhere.
However, you can always just limit it in software. Total "brightness budget" for the display, scale everything to dimmer if exceeded.