Unfortunately we don't have this information, but you might be more likely to find 'Antietam Blush' online (instead of at a local garden center), from one of the mail-order suppliers that focuses on fruits. If a web search for that cultivar doesn't turn up much in the way of listings, it might not be in general production yet: nurseries need to build up stock after a new varieties enters the market, and that can take several years for grafted fruit trees.

We had a question about sourcing this variety last year, and at the time found that 'Antietam Blush' was available from Cummins Nursery (New York), as an example. Adams County Nursery (Pennsylvania) is another example of a regional tree fruit nursery, though Extension doesn't maintain a list of nurseries in the region or what they stock, nor do we recommend any particular business over another.

Miri