"Gooseneck" usually implies something stiff enough to hold its shape--so things like task lights and microphones that need to be repositionable but stay where you put them.
A useful term is 'corrugated sleeving':
https://www.mcmaster.com/sleeves/corrugated-sleeving-6/If you don't need the cable to be fully enclosed by the spiral wrap, another option would be to buy some extension spring stock. It's available in long lengths so that you can cut it and form loops on the ends to create extension springs of arbitrary length. You can expand the helix by stretching it to just past its yield point so that it plastically deforms, which will make it longer, easier to get it onto the cable, and leave the cable more flexible once its installed. The main problem with this might be finding the spring stock in a suitable alloy/plating, usually I've only seen it in bare steel which will be prone to corrosion if not cared for.
You could form your own coil from suitable wire stock, it will take some trial and error to get the coil formed to the right diameter (you have to account for the spring-back of the material) and it can be tricky to produce a consistent coil, but you can then customize the size/helix angle/material to your needs. I saw a video a while ago of a model engine someone was building where they did exactly this to reinforce some rubber hose, with a nice little jig for forming a consistent coil, but I can't figure out the right search terms to find it at the moment.