Agreed; compression tops/garments hurt more than they are worth. "42C" on a man is hard to quantify without a photo or additional details; do you feel that you have "true" or "pseudo" gyne? Either way you deserve to be comfortable, this is not a leading question.
I'm certified as "pseudo" but I also tend to carry any extra weight I have in my chest before anywhere else (which sucks). I have a drawer full of compression tops/sports bras/tanks that I enjoy wearing and make me feel good/comfortable with myself, but my wife was never that supportive of this behavior other than when I was at my "peak boobs" stage around a year and a half ago. I'm 25lbs lighter now and yeah, I still have boobs and still prefer support
Most of the folks out here have legitimate gyne, and their needs may differ from yours. From what I've seen to date, "42C" is more likely to be chest fat/"pseudo" for a man. This is not intended as any manner of insult; boobs are boobs, right?
I suggest a proper medical evaluation to find out exactly what's going on before changing anything. If you have legitimate glandular tissue in play, you will need a legitimate bra for support or surgery to remove it. If you happen to simply store fat in your chest really well like me, there are maybe some better options for concealing that fat if that's what you want to do -- in my opinion male compression shirts assume you have a belly fat problem, not a chest fat problem.
If an immediate short-medium term "pseudo" garment proposal is needed; I suggest having a look at what Oalka has to offer on Amazon. They make a great medium-impact Sports Bra that will smush you up pretty well but is likely to be a tad noticeable under a T-shirt, but they also have a newer low-impact longline Yoga Bra that incorporates a tank over it. I like the longline Yoga Bra the best; even my wife didn't seem to notice it. It's very comfortable, but I must admit wearing "layers" is difficult on a 98 degree day for a man ...