You already have a lot of good, useful information, but I figured I'd chime in as well. Due to back problems, I was only able to bind sparingly prior to my top surgery. As a teenager, I used two, slightly tight sports bras (one facing forward, one facing backward) to bind my D-sized chest. This worked well enough as pecs or a fatty, male chest without causing increased back pain/other issues. Unfortunately, as a man who had an odd band-cup ratio (though not as extreme as yours), I understand how difficult it can be to find discreet sports bras that fit properly for binding. I also have no idea how safe or unsafe my binding method was, especially with my preexisting back problems.
I got my first, real binder in June of last year for my courthouse wedding, and have only worn it a handful of times since then. I think the longest I wore it was 5-6 hours on my wedding day, which wasn't particularly comfortable (due to my back), but also wasn't painful. Any well-made, appropriately-sized binder shouldn't cause pain or major discomfort, especially when worn as infrequently as you intend to.
I'm a big fan of GC2B, and their binders come in two styles: half-tank, which is similar to a wide-strapped sports bra, and full tank, which looks like a fitted tank top. They come in neutral, bright, and "nude" colors (eleven total) and are reasonably priced (in my opinion). They're also a trans-owned company, which is always nice to buy from.
I hope you find the right binder(s) for you!

- Alexander