I guess I’m an even poorer man. I just made mine from a cut off piece of PU foam. Cut a 90* angle in to it, and shove a pencil through at 1/4", 1/2", 1", 1.5", and 2". Works for cutlaps and any rail bands I ever feel like marking.
On all these tools, they make straighter lines if you keep a smaller bit of the pencil poking out. Less wobble angle. I only poke it out a tiny bit.