The only way I can think of is to duplicate the page.php and name it as a page template and put that into “page-templates” folder. Make sure you follow the WordPress page template standards (refer to their documentation for making templates. Open one of the theme’s templates and at the top, look at how the “Template Name: ” part was done (this is important so it shows up in the page templates list).
You would then have to change the classes of both the main content and sidebar containers:
span8 to be span7
span4 to be span5
This would increase your right sidebar and decrease the main content column. Then for the page in question, use your new template for the page you need it for.