A robotic fish accepted by animals as conspecifics is a very powerful tool in behavioral biology. To obtain the acceptance of the device towards the animals, it should generate some visual stimuli that can be perceived by a living fish as attractive signals. In this paper we introduce a novel design of a robotic fish lure based on a Rigid-Flex Printed Circuit Board (PCB) for experiments on the fish collective behavior. The 3D scan of a zebrafish Danio Rerio, a model animal for fish behavior studies, was used to mimick the main visual features of the zebrafish on the design. The robot can generate different stimuli thanks to its actuated caudal peduncle and two Light- Emitting Diodes (LEDs) placed near its eyes. The prototype has a total length of 63 mm and is only 1.5 times bigger than a zebrafish. The final prototype is waterproof and functional and thus satisfies the necessary conditions for the next steps that will be interaction experiments between the device and living zebrafish.