When I was cycling [many moons ago ! ] we used to be able to buy brake and gear cable, by the yard and the outer covering in any colour we wanted. Not anymore !, when I went looking for some in the local “bike shop”, I was offered only short lengths in a plastic bag at mad money. They were too short for what I had in mind, so that job went on the back burner. Bowden cable is available from suppliers in England, but like most things from there these days, the cost is way out.
Strange to say, I found short lengths for sale in what we used to call “The Pound Shop”, too short for my needs, but might do for other jobs, cheaper too !