Look for something with one inch side, lined front and waist draw string. You are liable to need a front pouch of some sort to provide accommodation. These are real swim briefs rather than fashion bikinis.
These are all Chinese brands and come a couple of sizes small.
Desmiit
https://www.ebay.co.uk/itm/Desmiit-M...Nw5_ 6stYFgAA
Seobean
https://www.ebay.co.uk/itm/Seobean-N...mra7eBd3ftlQnA
https://www.ebay.co.uk/itm/Seobean-N...oOwq 7l0xOd_Q
Brave Person
https://www.ebay.co.uk/itm/New-men-s...482ac654d35f10