I like the QuiltTak - last I heard, the company was in Alaska. If you use a good quality gun - NOT the Dritz or June Tailor - the hole will be no bigger than that of a safety pin.
For a grid, I went to the big home store (Menards, Home Depot, Lowes, whatever) and bought a ceiling panel - the kind used over lights in suspended ceilings. I think it was $6. It was only 1/4" thick (it really needs to be thicker!), so I cut the 24" X 48" panel in half crosswise and stacked the two halves. I glued them with model airplane glue (intended for plastic) and ended up with a 24" x 24" grid for a MUCH lower price than you would pay for a smaller one at the fabric store. I like it a lot.