September 1, 1917. This one was produced by Pictorial Review.
The Red Cross seems to have allowed all the pattern companies to produce patterns for them. Thus far we've seen the Matinee Blouse published by Home Pattern Company, the comfort kit by May Manton (though this may not be an Official ARC pattern), a taped hospital shirt by McCalls, and drawers by Butterick.
All the patterns sold for ten cents.
According to Priscilla War Work Book, Comforts for Soldiers and Sailors (available in facsimile from IvaRose):
Patterns and materials may be procured from most retail dry-goods stores, or through the nearest Red Cross Chapter. Simply ask for "Red Cross Pattern" for the garments you desire to make.
On the same page, recommended fabrics for the pajamas are:
...cotton oxford (cheviot) or equivalent. Seersucker "Bates" or equivalent. Outing flannel: "Amoskeag 1921"...or equivalent. Gray recommended.
The pattern envelope recommends outing flannel in light or dark stripes. Grey hospital pajamas is such a depressing thought.