If you like the idea of coco, consider Reptichip's "Microchip" size. I use it for neonate rainbow boas.
A fine-particle option that is better than coco is Zilla's "Jungle Mix". It is less dusty than coco fiber, and doesn't seem to have the ingestion/impaction risk of coco fiber, and handles moisture better.
Neither of these options have the main advantage of coco fiber, though, which is low price. Functional, cheap -- pick one.