I just found out how to make a watch file that works with python3-pyelliptic. As it turns out, the maintainer uploads releases to PyPI, so a watch file can be generated. I've had to change the version number of the .orig.tar.gz, as I'm using one made from a git snapshot. (I can't use the given tarball because the OpenSSL exception was not yet granted in that.) I've uploaded the version with the watch file to mentors.