I need some forwarding script

You can always use a meta refresh. I understand some people have reservations about it due to something the SEs do, but it’s a decent stopgap until you get something better.

I haven’t any idea how to actually write it – should be able to do a google search on “meta-refresh” and find something in the first few hits.

Alternatively, ask your host to write something into your .htaccess for you.

Add this to the .htaccess file in your WordPress directory (replace the last URL with the URL of your blog’s index.php file). If one is no .htaccess file there, create it with a plain text editor.

Redirect permanent index.html https://www.yoursite.com/wordpress/index.php

Ensure that there is only one space between the old relative URL (index.html) and the new absolute URL (index.php). The forum’s formatting is forcing it to a new line.

if your host uses Cpanel, they might have an easy way to do this using the “redirects” feature.
I had this same problem, and redirected the original index.html to my new WP index.php