Sorry don't know the names of the rulers.
To make your own, depending on how big you need the circles, I'd use either plastic template sheets or if they are to large for that, posterboard. I'd make a complete circle then quarter it.
Determine your size, cut a length of yarn, string, whatever you have, with enough to hold at one end, maybe use a push pin to anchor the center, pull taunt, then trace the circle shape from the other end, taped to a pencil. Just cut out shape, and quarter. Cheap templates.
Or if you have a plate that's the same size or any thing else laying around the house that could be used similarly.
Hope this helps. Sorry if I was confusing.