I know a few good batters from the Atkins quick and easy book, not sure how well they would work with rings though.

Basicly any combination of soy flour, ground sesame seeds, ground pork rinds, ground flax seeds.

The most low carb high fiber would be the Flax and Pork rinds.

Atkins also has some kind of tempura batter that might work. Havn't tried it though and not sure if it is ok in Induction.