We'll create fresh WordPress site with Product Notifier installed. You have 20 minutes to test the plugin after that site we'll be deleted.
Product Notifier is an free plugin that allow user to display message/notification on product single template.You can easily enable/disable notifcation from backend option.
User would be able to set different message for each single product page/template.
This is a lightweight plugin that you can easily integrate with one click.
wp-content/plugins/
directory of your WordPress site.product-notifier
from Plugins page