I have also gone to Quilter's Rule for Rhonda's rulers. I have her medium and large crescent and the medium S curve.
My go to straight edge is 3" by 6" and etched with 1/4 and 1/2" as well as a 45 degree angle. It is my most favorite ruler but has been discontinued (was made by Willow leaf studios) For a straight edge don't get anything bigger than 6" long as longer can be difficult to control.
For circles I bought from here:
http://www.deepbluetemplates.com/Lon...tes-s/1896.htm most reasonable prices EVER! Not etched with as many registration marks as I would like but worth it just the same. Can always do my own marks with an exacto knife.
You can always go to Home Depot or Lowes and have them cut 1/4 plexi for you too but you won't get the etched registration marks.