How do I tell my mom I want a bra in disguise?

I want to have a bra. I am 9 years old. How do I tell my mom in disguise?

What do you mean "in disguise"? You put on a mask and ask.

Seriously, at 9 it is unlikely you need one. But if you do, you go to mom in private, show her how you are developing and ask if you can go shopping for a bra.

When she takes you shopping at Wal Marts or other department store you take her to the bra section.

You want a bra in disguise? I don't get it.

Here's what sticks out in your question. You don't say you need a bra, you say you want one. So it's unlikely that mom will agree to get you one at the age of 9 if you don't need one.