Where can I can I get these?

[Torchwatch]

We've seen these before, always in black, always from the front view and never with a brand logo showing.
I'd suggest they have been custom made for photo shoots.
It doesn't really matter what happens at the back, it could be anything from a thong to a full back but it will show a lot of nether cleavage, half your bum will be showing above the suit, and you will experience tunnelling (a visible passage between the suit and your ass crack) as the suit will sit really low.
If you actually dive, kick turn or swim it this suit it would probably slide down your legs, it is purely for show and only from the front.
I think I could make one if I tried.

[BikenSwim]

Those suits are so low, they just have everything drooping below. I have a comfortable black Neoprene Koala Swim Diver Suit that hides everything below, but the sides have to come higher on my hips so the suit can stay on in the ocean surf. I also have a BBlair thong in Blue.

[Jack Lewis]

Hm maybe - here are some not in black. I've got an idea they're wearing girl's bikini bottoms (and have small dicks) - certainly can't find anything like it even on the Asian sites...

[BikenSwim]

AQUX used to have low-cut flat front suits, here's an old photo from their gallery https://www.aqux.net/gallery?lightbox=dataItem-ipaq9slh
Now they have more pouch suits for the international market.