i'd say a small gourami... a brightly-coloured dwarf gourami or a honey gourami. honeys are my favourite... and they stay really tiny, only around 2-3" so that would be fine.
or you could get a couple otos, but that would leave you with no brightly-coloured fish.
even a female betta... they make good community fish and come in the same colours that the males do... you just have to look a little harder to find a pretty female. a male might be okay, but i wouldn't risk putting a male with the zebras because they can be aggressive toward any other fish, so unless you know the personality of that particular betta (by putting it in a tank next to the zebras and see if he shows aggression) i wouldn't just throw one in there.
you can feed the corys whatever kind of frozen foods you feed anybody else, just put it to the bottom with a turkey baster. live brine shrimp are also favourites of most fish, but they don't have much nutritional value, so keep it to a treat only.