NGINX - proxying to a different Wordpress site while retaining URL - wordpress

Question

I currently have two WORDPRESS websites sitting behind an NGINX proxy cache:
htxtp://local.example.com
htxtp://local.example.org
I want to access a URL from the first site but serve it from the second site whilst not losing the URL structure of the first (to allow website2.com to see the website1.com cookies).
For example:
I want:
htxtp://local.example.com/somepage/
To proxy the page built at:
htxtp://local.example.org/somepage/
BUT I don't want the URL to BE htxtp://local.website2.com.
My NGINX config is as follows:
server {
listen 80;
server_name local.example.com;
access_log logs/local.example.com.access.log;
error_log logs/local.example.com.error.log;
location /somepage {
proxy_pass http://localhost:8080;
proxy_redirect off;
proxy_buffering off;
proxy_set_header Host local.example.org;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}
location / {
proxy_pass http://localhost:8080;
proxy_redirect off;
proxy_buffering off;
proxy_set_header Host local.example.com;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}
}
Any suggestions? I am trying to work out where the actual redirect is happening.