Did you know that you can use SSL for domains on a Shared IP? As long as you have Centos 6 (released the 10th of July 2011) or higher, you are good because your server would be able to support SNI which will allow you to install multiple certificates on a shared IP address. If your server is on a previous version, kindly ask your hosting provider to upgrade you.
If that is not a option or there will be hefty fees for the upgrade as you have to change hosting plans, it might be time to switch to another hosting provider.