One way to get a free SSL is to migrate DNS control of your domains to CloudFlare. By default CloudFlare offers a free "Universal SSL". Under the "crypto" menu select "Full" for the SSL box.
The process takes 24 hours before your certificate works consistently. After 24 hours have passed you can force your website to only be accessed through https. This option is found under page rules. You'll want to create two rules for your non-ssl url: http://yourdomain.com and http://www.yourdomain.com and turn on "Always use https".
If you don't wait to turn on forced https your website will work intermittently for 24 hours in 30 minute intervals. But don't worry, it will start working tomorrow!