You can setup your ssl vhost, as a ssl reverse proxy for the backend server running on port 9999. Depending on how you've setup the ssl example.com vhost you may try something like this:
Code:
<VirtualHost *:443>
ServerName example.com
--normal SSL stuff--
SSLProxyEngine On
ProxyPreserveHost Off
ProxyRequests Off
ProxyPass /simplecontrolpanel/ https://example.com:9999/
ProxyPassReverse /simplecontrolpanel/ https://example.com:9999/
</VirtualHost>