Wow, I too am planning a fretless, 5 string, short scale, somewhat headless, strung with tapewounds build.
I want to go E-C so I bought a 4 string set of d'addario short scale tapes and then found a site selling individual strings so I was able to buy a high C.
The fun of making guitars is that you can make things that you can't find for sale anywhere else, but it does mean that sourcing parts at the beginning can be an absolute nuisance 😁
Good luck with the build! Watching with interest.