I don't know about bars, but I have a good one for brownies.
1 cup oat flour (you can grind up oats in the blender)
1 cup unsweetened apple sauce
1 tsp baking soda
5 egg whites
3 scoops of chocolate protein powder
3 Tbs cocoa powder
1/4 cup stevia
spray a brownie pan with butter spray
cook for 12-15 minutes at 350
I take them out when they aren't quite fully cooked so they are moist
I noticed that different kinds of protein (isolate, concentrate, casien, egg...) yield different results so play with it
You can add raisins, nuts, or I like to add unsweetened carob chips. Sometimes I frost them with natural peanut butter.