Using computer-aided design and 3D printing within a co-design process to produce assistive technology (AT) has a positive impact in delivering customised solutions to end-users' needs. However, to date its adoption within healthcare services has been limited. This work aims to gather clinicians' insights to identify and analyse barriers inherent in the AT design, manufacturing, and provision processes and inform a detailed understanding of the current AT eco-system. It forms part of a long-term ambition to efficiently scale up a service for the co-design of custom AT across specialties and healthcare services. Five interactive workshops were run with 21 healthcare professionals currently involved in AT provision. Participants were recruited from two health boards in the UK. Thematic analysis was used to identify common barriers to scaling up a custom AT approach. Additionally, an eco-system map was created to determine the key stakeholders and their interactions. Nineteen descriptive themes, grouped into four analytical themes, were identified related to the design of AT, access to AT, healthcare staffing and healthcare system pressures. The eco-system map identified sixteen individual stakeholders and ten different groups of significant corporate stakeholders. The identified barriers relate to both the provision of off-the-shelf and the co-design of customised AT. Further promoting the scaling up of a co-design custom AT process requires: improving communication between stakeholders, enabling information about AT to be easily accessible, ensuring feedback is gathered and used, and creating tools that enable non-expert designers to modify custom AT designs safely and effectively.