@Ken g6 I need to find a UK source, but it also seems tricky to find such a cable but say 3 metres in length. I’m wondering if this:
Shop 2 Pcs USB C to DC 5.5mm x 2.1mm Power Adapter, Type C Female to DC5521 Male Connector, PD100W USB C Power Adapter, Waterproof Replacement Cable, Compatible with Mini Satellite Terminal. Free delivery and returns on eligible orders.
www.amazon.co.uk
combined with whatever length USB-PD cable I need might be the way to go (though I’d be much happier if I could find products with trustworthy names and/or lots of reviews!). Thanks for your idea!