Farmor15 have a look at Etsy. I know this isn't the same but someone on there may make them for men. My grandson's are tall and skinny and there trousers and jeans fall down builders bum all the time. I found a site on Etsy which made adjustable belts and braces for children. Full adjustable belts. Ones that just went on to back threw the loops and ones that went ones that went just on each side . All adjustable using poppers. Don't know if this is of any use.
My late husband was slim but had his trouser waists altered to fit. He weight always stayed within half a stone .