The swim bikini is high waisted and therefore an older design to the modern low waist Japanese design currently in fashion.
I immediately thought of Kiniki here in the UK and came up with these on Amazon UK:
https://www.amazon.co.uk/Kiniki-Rivi...+mens+swimwear
Or maybe these:
https://www.amazon.co.uk/Kiniki-Braz...+mens+swimwear
Other colours are available.