I found TrueGrips at my quilting store. They are flat donut shaped circles and keep the ruler close to the fabric. There is a website
www.graceframe.com listed on the back and a phone # 1-800-264-0644. The price on the front is $3.00. There is a sheet of 15 and I don't remember if there were more. They are made by 3M and may be found in the scrapbooking area at JoAnn's. I haven't looked. I was not that impressed with Invisigrip.