I'm not non-binary, but I've seen from other people that you can use a couple of sports bras
I don't have to deal with it, since I'm biologically male, but I'll help in whatever way you might need
I recommend layering sports bras or cutting a hole in the crotch of some control top tights for your head and cut off the legs of them so you can wear it like a top.
So I have a question for the community (specifically the non binary people) I want t get a binder, but I am broke, and afraid to ask my parents. Do you guys have any suggestions?