There is an Israeli company/startup that specialized in this - Brayola - they recently got sold to another company (try Google them) - partnering / using their service would be one of your best options because otherwise you have to create your own system/technology which is both costly and time consuming because (as you said) each company/country has it's own sizes.
I've successfully helped over 300 entrepreneurs, startups and businesses, and I would be happy to help you. After scheduling a call, please send me some background information so that I can prepare in advance - thus giving you maximum value for your money. Take a look at the great reviews I’ve received: https://clarity.fm/assafben-david

There is a way to get information about measurement systems of these countries and use it for setting sizes