We haven't found a good substitute for Shaoxing wine. We use it in many recipes and it will keep for a long time in the refrigerator. I recommend visiting a Chinese market and picking up a bottle. It's available online but more expensive. Go to a shop if you can. This recipe will still be delicious without it, so don't let that hold you back. If anything you can skip the Shaoxing wine (for this recipe, skipping is better than using a substitute ingredient).