I wrote an asp.net web app which uses SMO against SQL Server 2008 to be able to run some DB scripts. It references these assemblies (in the C:\\Program Files\\Microsoft SQL
To get this dll, you will need to install the Microsoft SQL Server 2008 Management Objects (available from here). That particular dll gets installed into the GAC, which is why you probably cannot find it using a search.
As you are using a hosting provider, it would appear that they do not have this installed. Your choices are to get it installed by them (which is probably unlikely), or deploy the dll manually (which may be on dodgy licencing ground).