May be worth clarifying first with the prospective sponsor if it really needs a “Policy” (implying a department’s worth of procedures not really needed or practicable), or a simple Rule?
The latter something like:
“Membership is open to all with an interest in [model-engineering and related interests]; irrespective of ethnicity, sex, sexual orientation, disability or religion”.
A good many clubs have such a rule, useful as a template even if the hobby itself is different, hence my brackets.
Though the prospective sponsor might ask how your facilities cope with a disabled person – at simplest, door ramps rather than steps, and unisex lavatory or lavatories suitable for a person using crutches or a wheel-chair.