Hi Traci. You can get the split rings just about anywhere you can get new keys cut. But I do find them pricey if you're buying a lot of them (about 50 cents a piece). If you need larger quantities, I recommend the craft store, you can find them in the jewelry section where all the other findings are. You can usually get them in bags of 20 or 25 for about $5. I shop at Hobby Lobby a lot and their findings go on sale for 50% off every other week, so try them if you have one near you.
Nicole Marie it was sooooo long that I made this video that I can't remember the size I used. But you should just use your eye-screw as a guide and use whatever fits on the shank. Have fun!