There is a way through a method called comment selling. There are two companies in this space. One is called Soldsie and the other is called Comment Sold. This triggers an invoice to them via email when they comment on your t-shirt post. They say "sold" in the comment and get an invoice delivered to their inbox. It's really cool. It's not via DM, but it's another way to sell on social media without having an eCommerce site.