In reply to nikkormat:
As a general rule isometric exercises are considered safer than movement based exercise. Not sure which would be best to avoid lower abs but there are a ton of isometric core exercises like plank variations, side planks, L sits, V sits, superman, and progressing into things like planches, levers etc. These will all be safer still if you back off on intensity and focus on perfect form until you feel able to push harder.
Also worth considering that you might not want to avoid lower ab stuff completely. If you do then you'll end up with a weak area relative to the rest of your core and that will be more susceptible to injury when you start training harder again.
For movement based exercise windshield wipers don't seem very lower ab intensive. Not so sure about hanging wipers though. Check Youtube. Lots of good trainer videos many of which are very specific about the muscles each exercise trains.