Migrating SSL key to new box

We just recently upgrade a client from v9 to v11 and I wanted to move their SSL cert to the new box. When I went to import the cert on the new box it said it was missing the private key (makes sense).

After fiddling around I discovered that the file /etc/apache2/ssl/apache.pem contains the cert key so I copied that over to the new box and restarted apache and boom, ssl cert was working.

The problem I'm having is that on reboot it appears that the apache.pem file gets overwritten or something because it goes back to the self signed. It is a simple fix to replace the file and restart apache but I'd love to just have it stick on reboot.

So the question: how do I keep the apache.pem file from getting overwritten on reboot (or if it is copied from a different location, where is that so I can overwrite that file with the proper one)?

Alternatively: can we get an SSL export feature so we can move the certs to new/different boxes?

Disclaimer: yes I now I can generate a new CSR and submit for a reissue but that can take some time and on occasion you have to jump through hoops so I'd like to leave that as a last resort.