You could most likely "get away" with T-Kingdom, but keep in mind that their products are much more expensive while getting you less.
I would *definitely* not use a non-stretch band of fabric around your rib cage. This is a *very* bad idea. Even a tight sports' bra or two would be so much better.
Have you tried out any sports' bras ? Try on a few different sizes at the store - if you're an A, you might easily find something that works great for you. Look at the heavier-duty sports' bras, the ones meant to be able to be worn on their own.
I wouldn't pay T-Kingdom prices when you could probably get a sports' bra that works just fine. The tri-top might be overkill, but it's much less expensive and you could add your own zipper or heavy-duty velcro if you wanted that to it.