What a cutie! I have boy clothing that is custom made
MACHO WEAR
You can also find cute little boy clothes at WM or target.
I know there is a video on making a little shirt out of a sock floating around too. He will grow fast so if you need something quickly, just take a sock and cut off the toe and add 2 arm holes. Cut the length as you need. It will work in a pinch until you can find something!
Good luck!!