We do theater. My husband and I met in college doing theater and we have been lucky enough that we have been working in the theater ever since. My husband works for a huge summer theater program and we try to support the shows and now mini-me is stuck doing the same.
Sometimes there are smaller sizes but this time the smallest they had were children size 10-12 shirts. Obviously too big for our 2T girl.
I laid a favorite tank dress on top of the tee-shirt and cut the sides and arm holes from the A-line the dress provided. I did a quick stitching with a stretch stitch up the sides on my machine. I used the finished edges of the sleeves and added some ruffle for the smaller arm hole size and was able to sew it very quickly into a shirt that fit much better. And she was pleased!
Here you can see the sleeves pretty well. I replaced the boring white buttons with strawberry buttons which she loved.
You can see the dress is a little long, I used the finished edge of the tee shirt as the bottom . If the artwork had given me room I would have trimmed a few inches off and added a ruffle, but the art was so close the bottom and moving the neckline would be way too much work. Hey, maybe this way it will still fit her for our trip to Disney next fall!