This video shows how to bind with a swimsuit. Just thought I'd share. So if you live with parents or something, you could say you're swimming and you need two swimsuits to rotate; then you can turn one into a binder and nobody will be the wiser.
At least older, unknowing parents are unaware of trans issues, so they probably won't sneak a second eye if you say it's for a school project or Halloween (an actual binder). I guess that's just in my experience, makeup for me is actually fairly easy to get if I play my cards right.