Reverse proxy in subdirectory can't find static assets

Question

I'm using Nginx as a reverse proxy to route requests to localhost to my node server, but requests to localhost/blog to a ghost server (a blogging platform)

My Nginx config is like this:

server {
    listen 80;

    server_name localhost;

    location / {
        proxy_pass http://127.0.0.1:3000;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection 'upgrade';
        proxy_set_header Host $host;
        proxy_cache_bypass $http_upgrade;
    }

    location ^~ /blog {
        rewrite /blog/(.*) /$1 break;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $http_host;
        proxy_set_header X-NginX-Proxy true;

        proxy_pass http://127.0.0.1:2368;
        proxy_redirect off;
    }
}

edit: The reason I'm rewriting the URL with rewrite /blog/(.*) /$1 break; is so that the ghost server doesn't get the request to /blog/, which it can't use

However because ghost, the blogging platform, is designed to be run in the root directory, all static assets fail because they should be going to localhost/blog/static/asset/path rather than localhost/static/asset/path:

Is there any simple solution to this problem? Or do I have to rewrite all the HTML for ghost?