I have been on the hunt for a 3" square ruler for trimming up 2.5" (finished) half square triangles. I never would have thought that they would be so hard to find. Needless to say, my search has been fruitless... until I found a site that will custom laser cut and engrave pretty much any size acrylic shapes. So I ordered these.
I haven't had a chance to use them yet as they came in the mail the day before I left to Indiana.
The price was very reasonable, including shipping it was only a couple dollars more than the cost of a 12 1/2" square ruler. Shipping time was good, I received them in less than 10 days.
I did not think to ask them if it would be okay to link to their website, so for now if you would like info please email me and I will be glad to forward the info to you.
UPDATE: To celebrate the Black Friday Sew In (#BFSI) I would like to give away a set of these trimming squares. So if you would like a set please comment on this post or follow me on twitter @SweetAdelineQ for a chance to win. I will choose a winner at random at midnight tonight (eastern time) and contact you by email for shipping info.