Efforts to promote inclusive and sustainable cultural change in physics departments require reliable tools to measure progress. This paper describes the co-design and development of two survey instruments to assess departmental culture regarding inclusion and systemic change. Using human-centered design principles, we brought together stakeholders from physics and astronomy education in a series of facilitated co-design sessions. These collaborative discussions informed the survey constructs, representation of results, and alignment with users' values and goals. We detail our facilitation strategies and co-design activities, showing how this approach built consensus around key constructs for measuring cultural change. We also reflect on lessons learned and provide recommendations for others interested in using collaborative design to create tools that support and measure change. This work contributes to the growing practice of involving participants directly in the development of survey instruments. By centering users' experiences, we aim to support more effective and inclusive approaches to evaluating and advancing departmental change.