[u][/u]I have seen duct tape used in place of grommets. You can take a narrow strip of duct tape and put it on one side, twist it over (so it does not stick together) and apply it to the other side to form a loop you can put a string through. I like the idea of wrapping a small stone in the corner because it stresses the material more evenly than a grommet. Food for thought anyway.
Jim M