This is a simple DIY project that you can complete in 15 minutes. Buy a shower curtain and a set of hooks. Place the shower curtain hooks on curtain and hang over your shower. Once the shower curtain is in the perfect place, mark on the curtain your cut line. Make your cut line where the door meets the side. Remove the shower curtain. Lay flat on a surface and cut a straight line on your cut mark. Thus, cutting your shower curtain into 2 pieces, but not of equal size.
You can sew the raw edges back to make a more finished look, or you can use liquid stitch(if you don't have your sewing machine) to finish off the edges. Now, take the small part of the curtain, hook on curtain hooks and put into place. Next, hang the larger portion of the shower curtain on the hooks over the top of the shower. Once you are in the shower, pull on the end curtain hook that is attached to the larger curtain piece and pull to cover the glass door. People can now pass through, etc while you are in the shower. WHEW!