My advice is similiar to posts already up. I was on HRT for several years before transitioning in the workplace, but I hadn't started anti-androgens until the last couple of years. And Anti-Androgens are what kicked breast growth into overdrive (if you are one of the lucky ones that have that 'gene'). It became exceedingly hard to hide the growth.
They were hot, especially in summer, but I used these chest binders to good effect:
Sold by a company called underworks in the states. (google 'em if you are interested).
Style #991. But I don't remember them being so expensive back then. I bought 5 of them to last through the work week, and wore them for a couple years, they are sturdy.
I'd donate the ones I had to the cause, but once I transitioned out, they went into the trash, they were a bit worn, anyway.
In the end, when I asked people if they ever noticed, no one did. Even the last three months, when I decided to chuck the binder, and just free form it under my loose dress shirts (with a t-shirt underneath), no one noticed. They just don't expect to see things that aren't "supposed" to be there,
.
Good Luck Galantha!
*huggs*,
Melan