Hi Alex,
I'm not a Mac user, so keep all the following infos
with a pinch of salt.
have you tried the Homebrew distro [1] ?
it seem to support both spatialite-tools 4.3.0 and
spatialite_gui 1.7.3
the alternative MacPorts distro [2] apparently
seems to support just spatialite 4.3.0 and
spatialite-tools 4.3.0, but I was unable to
find any reference to spatialite_gui.
have a good luck,
Sandro
[1]
https://brew.sh/
[2]
https://www.macports.org/