Based on Parametric Pulley Library which in turn was based on Parametric Pulley, this tweak to the old pulley generator adds support for hexagonal holes with chamfer and an array of round holes in a pattern (common on hubs). The creation of this was inspired by this FRC-focused GT2 pulley collection.
The default configuration hides the usual built-in nut-based mount in favor of just the hex hole. The hex hole is sized for 1/2" hexagonal rod, and the hub hole pattern is that of the Vex VersaHub system. This makes the pulley well-suited to use in the FIRST Robotics Competition (FRC).
The generated pulleys are a collection ready for use with HTD 5mm pitch belts in either 9mm or 15mm width. The latter is what is commonly used on the FRC robot stock drivetrain, so FRC teams will likely have such belts lying around. Combine with 1/2" hex rods and you're in business. Hold in place with hex shaft collars (either the metal ones commonly used or 3D printed ones).