NGINX - Short domain proxy to full path on another domain - nginx

Question

I have two domains, let's say ex.io and example.com. I own both and have access to both servers. Both run NGINX.
Goal: I'd like to have any request from ex.io forward to a specific path under example.com, e.g. http://ex.io passes to https://example.com/foo/bar. This has to be done without a redirect (more in Context)
Context: The goal is to host a shell script at https://example.com/foo/bar so that curl ex.io | sh will run the shell script. I'd like no redirects to happen so no additional flags are needed for curl.
My current .conf setup for both servers follows:
server {
listen 80;
listen [::]:80;
server_name example.com
return 308 https://$host$request_uri;
}
server {
listen 80;
listen [::]:80;
server_name ex.io;
return 308 https://example.com/foo/bar;
}
# ...
This works, but requires the extra flag -L to run properly under curl. How can I proxy ex.io to go directly to https://example.io/foo/bar?
EDIT: I'm forwarding http://ex.io/ to https://example.com/foo/bar which may be tricky going from http to https. Bananenkönig's response fails with a 502 Bad Gateway error and the following logs:
2020/10/26 23:28:45 [error] 223#223: *281 SSL_do_handshake() failed (SSL: error:14094410:SSL routines:ssl3_read_bytes:sslv3 alert handshake failure:SSL alert number 40) while SSL handshaking to upstream, client: XXX.XXX.XXX.XXX, server: ex.io, request: "GET / HTTP/1.1", upstream: "https://XXX.XXX.XXX.XXX:443/foo/bar/", host: "ex.io"
2020/10/26 23:28:45 [warn] 223#223: *281 upstream server temporarily disabled while SSL handshaking to upstream, client: XXX.XXX.XXX.XXX, server: ex.io, request: "GET / HTTP/1.1", upstream: "https://XXX.XXX.XXX.XXX:443/foo/bar/", host: "ex.io"

Answer 1

I would try it like this:
server {
listen 80;
listen [::]:80;
server_name ex.io;
location /some/location/on/ex.io/ {
proxy_pass https://example.com/some/location/on/example.com/;
}
}
when you want ex.io/ (on location /) to be forwarded to example.com/... write "location / { "