Not sure about changing the permissions, which might negatively affect your security. But it would be possible to run a cron job to do that regularly, or copy the certs to a different directory.
Another way would be to use nginx as an SSL terminating proxy in front of the node.js app. Eg if the node app runs on port 8123 then get nginx to forward from 443 to 8123. There are examples of node.js nginx proxy templates in these forums.