We present a new version of tactile-sensing finger, GelSlim 3.0, which integrates the ability to sense high-resolution shape, force, and slip in a more compact form factor than previous implementations, designed for cluttered bin-picking scenarios. The novel design integrates real-time model-based algorithms to measure shape, estimate the 3-D contact force distribution, and detect incipient slip. The constraints imposed by the photometric stereo algorithm used for depth reconstruction and the implementation of a planar sensing surface make the miniaturization of previous designs nontrivial. To achieve a compact integration, we optimize the optical path from illumination source to camera. Using an optical simulation environment, we develop an illumination shaping lens and position the source LEDs and camera. The optimized optical configuration is integrated into a finger design composed of a robust and easily replaceable snap-to-fit fingertip module that facilitates manufacture, assembly, use, and repair. To stimulate future research in tactile-sensing and provide the robotics community access to a reliable and easily reproducible tactile finger with a diversity of sensing modalities, we open-source the design, fabrication methods, and software on Github.