In temperament I would think the Asian Glass Catfish would be very compatible although not South American like Discus.
What kind of catfish is eating your Neon Tetras? They can vary in what they will engulf depending on the species and therefore the mouth size. This would critically influence your choice of schooling fish though Glass Catfish are bigger than Neons.
What is the temperature as this can determine the suitability of fish kept together. Neons are best at a lower temperature than Discus from my experience. Glass Catfish may prefer a lower temperature than Discus, although slightly higher than Neon Tetras.
Discus tend to be kept at higher temperatures which may not suit many species that only encounter warmer conditions in the breeding season if at all. High temperatures may shorten the lifespans of fish that are not adapted to tolerate them all year round.
I look up the temperature range given on Seriously Fish though this may not give the full picture. I think it is a difficult subject to give precise information about.