Are there any 225 amp meter sockets?
You want a 200A meter socket in this case
The reason you're confused is because meter sockets are rated by their continuous ampacity, but panels and breakers are rated by their maximum nominal ampacity; this difference is most clear in Class 320 work, where a 320A continuous meter base is used either with a single 400A or a pair of 200A service disconnects.  As a result of this, a typical 200A meter socket is rated for 200A continuous, and thus will have no difficulty with a 225A service, provided your utility recognizes it as a valid service (not all utilities do!).