You can do stomach isometrics anytime. Just tighten up and pull in the stomach muscles, hold for 20-30 seconds, relax, and repeat. Do this a few times whenever you think about it during the day. There's all kinds of stomach exercises you can do - side bends, toe touches, side twists, cross body toe touches, leg raises, etc. Good luck! I'm in the same boat, trying to get into shape again, but I'd say you're in better condition that I am (trust me on that!).