Custom Google Search causing mixed content


I have google custom search installed and it works ok.

I have recently updated my site to use SSL and this has resulted in my site getting mixed content.

I understand that all HTTP needs to be changed to https.

My problem is I am having an issue with custom google search loading its stylesheet over HTTP and not https.

All other plugin stylesheets have adapted nicely, but not for custom google search.

I can tell that the error is from the linked stylesheet for the index.html that is loaded. See screenshot.

All I want to know where can I go to edit this file in my file manager or PHPMyAdmin.

All assistance is welcome.