Hey @Peter_Canada, great to see you on the forum! 
I know, Viator reviews would be a great addition to the widget, but I’m afraid that at the moment, we don’t see a quick solution for its implementation, I’m really sorry 
But, we’re on the verge of adding an option that will allow you to add reviews manually, regardless of the source. Perhaps it could work as a workaround 
Just in case, we post updates for this feature request here: Be able to manually add reviews to the All-In-One-Reviews + premoderation.