Hi there Mark!
In terms of manufacturing, the obvious people who might use a design like this would be brand who make musical instruments and other musical equipment.
They would be well placed to distribute and actually sell the capos.
Whoever would be producing it would need to use a 3D printer that can print using metals.
More and more 3D printers are being produced these days for printing in metals, such as in titanium.
Although these printers are still uncommon, so a product like this might be a little ahead of its time!