Half sizes for bigger plugs

Hey guys hows everyone doing? So curious question why does it seem like its so hard to find half sizes particularly like 14.5 mm and 15.5 mm for example?
Where can I find half size glass plugs for stretching to 14.5mm and beyond? They are damn near impossible to find I swear
I know what you’re thinking “just go up a whole size”
I could yeah
But Ive blown my ear oht before and my right ear has a problem and having different size gauges will bother me 😂