They always spawn hiding inside of herbs. See Red Velvet Flower for potential locations. They do not share spawn with Onyx Rabbits but might share with Brondie Kethus, so kill Brondie Kethus if you see them. They used to be easy to farm when there were multiple channels. My recommendation is to hunt them every 1.5+ hours since their respawn time is over an hour. I believe the zone has around 4 of them at a time and they drop 0-2 Full-Colored Leather.