I'd print out the page and any other contact info from that websight, then take it in to a dealer and ask him to order it. he should be able to handle it(and hopefully not stick you too hard on his fee), and if not point you to a local dealer who could.
also make sure the m1 is what you're looking for. it's barrel is about the same length as the 28 but looks shorter because of the grip style. the M1-sb has the shorter barrle with the same stock type.
just check through the para-ordinence sight and they have all the modles there.