Showing my age here.....in the 1970s when it was okay for US men to wear briefs to the pool, several manufactures including Jockey actively marketed underwear / swimwear products. They were typically a bikini format with about 1.5-2.0 inch sides, with a very light second layer at the crotch which I usually cut out.
i have an older DKNY thong you may like…gotta wait until next week when I’m home for a photo