There is a way to override the Antergos repo.
You can create your own local repo onto your hard disk, and put your AUR version of the vivaldi package there.
Then write info about your local repo into /etc/pacman.conf, just before the [antergos] repo definition.
The whole thing goes something like this:
- create your local repo directory (may want to select a better place…)
mkdir -p $HOME/myrepo
- download vivaldi PKGBUILD from AUR
yay -a -G vivaldi
cd vivaldi # yay downloaded PKGBUILD here
- move the built package to the repo
mv vivaldi-*.pkg.tar.xz ..
rm -rf vivaldi
repo-add myrepo.db.tar.xz *.pkg.tar.xz
- edit /etc/pacman.conf, add your new repo info (the following lines) before [antergos] (and change your username!)
Server = file:///home/<username>/myrepo
SigLevel = Optional
- and finally, run this (and pray ;))
If it worked, congratulations!
The only minor disadvantage is that when the AUR version changes, you have to build the package again, add it to your repo, and run pacman -Syyu.