All the kit for saw sharpening turned up in the mail: saw set, files, jointer. All that remained was a saw vise. So I made one.
I ripped a piece of poplar in half with a ripsaw and planed the sawn edge flat. This will be the vise jaw. I cut some uprights from some spare douglas fir and fit them to the vise jaw with a lap joint. I also cut some notches in the uprights so that it can be clamped into my workmate and not fall down when the pressure is released to move the saw. I also chamfered one side of the jaw to allow room for file movement.
There is a strip of wood linking the bottom of the uprights to keep them apart, and at rest the vise jaws have a very small gap between them. When I tightened the workmate vise the saw vise grips the saw tight. It is long enough to attend to a 28″ saw all at once.
Lastly, I made a pair of file guides in order to achieve a consistent rake when saw sharpening as suggested in this saw filing article. I made one at 5 degrees for the rip saw and one at 20 degrees for the crosscut.