The comodo SSL certs via https://ssls.com are very cheap. Install instructions for a Nginx based webstack:

Create signing request:

Copy paste the content of the csr on ssls.com, choose webserver other. Fill out the next page with info about your organisation.

You’ll receive a zip with a bunch of files. Copy the files to the webserver

Login on the server and go to /etc/nginx/ssl/example.com/ Now create the bundle_ssl.crt

Add to conf (I already had SSL running with fake certifcates):

More info: https://gist.github.com/bradmontgomery/6487319