Your provider has to enable the pdo_mysql drivers. That it isn't already available doesn't speak well for your provider. PDO isn't a whole lot of use without the mysql drivers.
On the internet I searched for you for a solution, but found nothing concrete. To be honest, I see limitation in the requirements of the cms software.
Alternatively, there are three options.
- Perhaps Modx also works with SQL lite. This is driver available.
- You can switch to a dedicated server, where you can decide to install appropriate software.
- Perhaps you can use another CMS like Joomla or Wordpress, which worked very well with our servers and your subscription.