NGINX frontending Kibana not working with “_plugin/kibana/” URL

I'm running the AWS Managed ElasticSearch to collect some logs and have created some Kibana dashboards to visualise the data, all that works fine.

Unfortunately the Kibana plugin included on with the AWS cluster is pretty much open to the world, so I have setup an NGINX reverse proxy to provide authenticated access. This is also working fine if I simply hit the domain URL and specify the full URI to the Kibana plugin. For example:

http://nginx.domain.com/_plugin/kibana/app/kibana works just fine, here in the nginx configuration I am using to achieve that:

worker_processes 1;
events {
worker_connections 1024;
}
http {
server {
listen 80;
server_name localhost;
location / {
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $remote_addr;
proxy_set_header Host $host;
proxy_set_header User-Agent $http_user_agent;
auth_basic_user_file /etc/nginx/.htpasswd;
auth_basic "Auth Required";
proxy_pass https://search-mystuff.ap-southeast-2.es.amazonaws.com/;
proxy_redirect https://search-mystuff.ap-southeast-2.es.amazonaws.com/ /;
proxy_set_header Authorization "";
proxy_hide_header Authorization;
}
}
}

Rather than providing the full URL, I would like to simply hit the base domain name of the NGINX server, which would then redirect me to the full Kibana URI. So what I would LIKE to do is this:

http://nginx.domain.com

After entering the above URL, I would like to be redirected to the full Kibana URI, so I would end up with a URL like this

http://nginx.domain.com/_plugin/kibana/app/kibana

Here is the nginx configuration I have tried (in various different permutations) that does not work:

worker_processes 1;
events {
worker_connections 1024;
}
http {
server {
listen 80;
server_name localhost;
location / {
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $remote_addr;
proxy_set_header Host $host;
proxy_set_header User-Agent $http_user_agent;
auth_basic_user_file /etc/nginx/.htpasswd;
auth_basic "Auth Required";
proxy_pass https://search-mystuff.ap-southeast-2.es.amazonaws.com/_plugin/kibana/app/kibana;
proxy_redirect https://search-mystuff.ap-southeast-2.es.amazonaws.com/_plugin/kibana/app/kibana /;
proxy_set_header Authorization "";
proxy_hide_header Authorization;
}
}
}

With the configuration above, when I browse to http://nginx.mydomain.com the URL is redirected to:

http://nginx.myaws.com.au/_plugin/kibana/app/kibana
This looks like it SHOULD work, however I receive an error in the browser window:

{"statusCode":404,"error":"Not Found"}

I have about 4 hours experience with nginx, so hopefully I'm missing something simple.

Any help would be very much appreciated, thank you!