@ninjateam Full disclosure: I'm working at Userlike, so I might be a bit biased ;)We have a lot of customers using our Squarespace plugin to chat with their visitors. Userlike is a free live chat plugin with plenty customization options and themes that you can easily add to your Squarespace site in under five minutes.
Take a look at our video tutorial to see how to add Userlike live chat to your Squarespace site: