Topic of badly fitting clothes: I need help!

I got the DFYNE L sports top with the halter neck bikini strap back and I got my boobs done. The top is an L and it's loose around me, but the coverage is not big enough for my boobs.

When I adjusted the top, I was cover but I didn't stay covered for long.

Really disappointed because I love the DFYNE look.

So where all are all the big boob bikini girls shopping for their gym tops?

My best finds have been: Shein and Primark but I don't want to support an ethical nightmare.