You don't need an extended license, it won't help in this case 🙂
One solution would be to have a separate search instance (shortcode) for each site, but if you have a lot of sub-sites, then this could get too complicated.
The only thing you need to change in that code is the placeholder variable. As you can see it is an associative array, where there is a text mapped to a specific blog ID – so in case of blog ID=1, the text after the 1: is used, for blog ID=2 the text after 2: and so on.. You can add as many lines to it as you need.
I hope this helps!Best,
If you like my products, don't forget to rate them on codecanyon :)