I believe that trying to find half pints from all fifty states could be quite difficult , they are usually hard to find , or at least they are in my area . Pints or quarts would probably be easier . I know a lady from here in Ohio that started out trying to collect all fifty states in pints , but gave up after a while and collected all of them in a mixture of pints and quarts , still took her quite a long time to complete the collection .
Many of the dairies from my area never used half pint bottles. I'm sure you would have no problem finding a half pint from each state, but I agree that pints will be easier to find. Just about every dairy had pints and quarts. ~Jim