With the effort involve in editing the entire template's/theme's source code to add additional left and right sidebars, I think the time taken to change and further personalize the theme would be better worth it than manually coding it. I don't think there's a plugin that would allow you to add left or right sidebars - if the template does not come with that source code, no plugins would be able to address that either. You can find many responsive templates that are free on their WP template database.