You could modify Avada’s templates for the posts, pages you want to display your special logo on, or you could override the template responsible for header or, even better, logo generation. This would require to provide a modified logo.php file at at /templates/logo.php in your child theme. You would add something like
if( is_page(array(64,65) ) )
$standard_logo[‘url’] = ‘/path/to/special-logo.png’;
Whether it is a pro or a con, you’d have to add page/post IDs to the arrays in the logo.php if you want to display the special logo on additional posts/pages later on. So this solution is not easily accessible for editors.
The general Idea here is to hide the actual logo and add a background-image to its container displaying the special logo. This would get quite fiddly with widths and heights regarding responsiveness. There is an old thread about that approach here.
So we want to create a Global Element in order to reuse the feature on every page necessary.