Transparency on Metahumans?

Is it possible to add transparency to Metahumans? I’ve googled for hours and not found any reference to this question. I need to give my Metahumans a stealth ability which will make them semi-transparent. I already have a Material Function that can do this to existing models, but at least some if not all Metahuman parts are made from Material Instances, not Materials, and I can’t see any way to add a Material Function to an existing Material Instance.

Please does anyone know if this is possible, or some other way to add transparency to Metahumans? I really need help and would be grateful for any input :slight_smile: