Since I'm doing a male cosplay soon I decided to invest in some real bust binders. My previous male cosplay, Napoleon, involved a binder I made myself out of 6" elastic, hook and eye tape, and plastic imitation whalebone. It ends up riding up and the bones dig into my underarm, so this time I went for some more comfortable options. I purchased these from http://www.lesloveboat.com.
First off, in my regular bra:
And a sports bra, which I've seen recommended:
Here's the Super Strength Velcro Short Binder:
The High Performance Velcro Short Binder:
And the Strapless Velcro Binder:
They're all very comfortable, and have a great result. I'm looking to get a compression shirt to wear over the last one, just to reduce the issue of side-boob under the arm, but in all I'm pretty happy with all of them, and I'll be putting the others into my kimono kit so I can wear kimono more comfortably!