My opinion is get your own SSL certificate, it gives your site a feel of professionalism and authenticity.
Many users will click on that certificate to verify who the certificate is issued to, and if they see a name which refers to another site, they may flee.
Getting an SSL certificate is so cheap that you should get your own.
You can visit my site to get yours or at least get a price;
http://www.foxtrotdomains.com