It is not possible to provide two domain names for the same Server IP address and get two different SSL certificates (one for each domain name).
It is however possible to get a Multi-Domain certificate, which is a single certificate containing more than one domain name, and that certificate is for a single server installation (most commonly used by hosting providers). For more information on this type of certificate please contact our sales team: http://www.instantssl.com/ssl-certificate-corporate/ssl-certificate-contact.html
Also note that the use of Host Headers (which is how you can use a single IP for more than one SSL enabled domain) is not recommended for E-Commerce sites.
Dependent on the domain names a Wildcard SSL might meet the requirements, these are however more expensive due to the unlimited number of sub-domains they can cover. For example, a Wildcard for *.mydomain.com can be used to have SSL on any site where the * is replaced by a name, i.e., 'secure.mydomain.com' or 'gb.mydomain.com', etc (there is no limit).
Please click to contact our sales team for more information on this type of SSL certificate