Sure, no worries. I like this kind of open ended stuff. It’s my favorite sort of thing.
If you simply want to take a distribution of sales for brand X and try to map the physical sizes of those objects (as say measured by a tape measure) to the nearest distribution of sizes in brand Y that gives closest agreement in physical sizes… this is perhaps a more concrete goal that people might help with. People tend to think that if you buy a 36x32 pair of pants from each brand, they should all be the same physical size… but that’s not true as I’m sure you know, “relaxed fit” vs “slim fit” and “big and tall” and “vanity sizing” are all things that vary from one mfg to another.