The white cloud mountain minnows would be better than neon tetras. The neons have occasionally been known to nip at long fins (definitely a bad thing) and they aren't quite as zippy as the minnows, who will be able to outswim your betta if he gets mean.
There are a few varieties of the white clouds. There's the standard white clouds, long fin white clouds, and (my favorite) golden white clouds. All of these would do best in a group of at least five because they like to school together like the neons.
I know you wanted to pass on the Otos, I just wanted to mention that I fed mine Zucchini and they loved it! You just boil a slice until it softens up some and put it in the tank with a veggie clip. I usually did that at night since they are more active at night, then I removed the zucchini the next day. It was A LOT less messy then the algae wafers. :)