I am informed that Cheaper Than Dirt, despite emailing everybody that they have 5.56 stripper clips in stock, still show them as backordered. May the fleas of a thousand camels infest their nostrils and camel spiders come to chew upon their lying entrails.
However, fear not. Courtesy of jeepster and others we have this better source.
Go here. Look under weapon categories and you will find both M14 and M16 ammunition repack components.
Old Sarge's Drop Zone has what you need.