Get an off-white Dockers type button down shirt ( all cotton) from value village/goodwill type second hand store. Trim off the button sections in front and shorten the sleeves. Do a quick hem on the edges, including the bottom edge.
If you can't sew, still cut the shirt to the little tyke's size and use fabric or hot glue for the hems.
Weather with coffee / tea stain...
and you can be off to Tosche station for some power converters.