The Vale belt is my narrowest option at 25mm (1") wide.
In recent years, narrow belts have been considered mainly to be women's belts, but there are plenty of historic and modern examples of men wearing them too. Gender isn't real anyway, so wear whatever you want to.
Made by hand in Oregon.
Belts are made-to-order and cannot be returned or exchanged, so it's vital that you get your sizing right!