I've researched this topic for years, and have come up with nothing. Russ tells me they may be called a top deck, p/n 6894-5, but I'm not convinced. I'm currently using a copy of a NOS 17-22 boot I made, but it doesn't cover the part of the top that goes down the rear bow socket completely. In addition, the rear curtains on the '22-5 cars have no eyelet in the center for a middle strap.
As far as I know the "top deck" is that part of your top that runs from the front bow to the rear bow.
As I recall the 22 top boot hasn't got three straps like earlier cars, just two, about 8 to 12 inch in from either side of the boot,
This one was out at the Long Beach Model T Swap Meet a couple of weeks ago (notice the two straps) and is correct for 1922-25...as far as I know....it's the one I'm going to copy at least.
The top boots sold by the vendors are absolutely incorrect in every way, shape and form including the manner in which they are installed on the car which is unfortunate because it is an item that could be very easily and correctly reproduced. The original drawings probably exist and there are enough surviving originals to use as examples.
The fasteners were eliminated by the 1917 model year if not earlier.
My used the original top boot on his 1917 up until about five years ago when he reproduced a new one himself.
I know of another person who reproduced a correct one for his 1915 touring (1915 includes the snaps).
Below is the original top boot from my dad's 1917 touring - the two outside straps are attached to the top side of the boot and go over the seat back. The middle strap is attached to the bottom side of the boot and is laced through a grommet in the rear curtain of the top and grommet in the top side of the boot before going over the seat back. Three short straps with buckles are screwed into the wood at the bottom of the seat back.
I've also seen an original roadster top boot that was the same as the touring boot below, except smaller.
My NOS boot that I used for a pattern is exactly like the one Erik posted above, except I had to leave the center eyelet out cause I'm using it on a '25. I did however, sew a center strap to the topside of the boot. I AGREE with Martin, that the top deck is the center piece of material that runs from the front to the back bow. BTW, the above boot was introduced in 1916.