Smart Pointer showing deep copy semantics

There are so many types of smart pointers around like shared_ptr,
unique_ptr, auto_ptr, each with their own set of benefits.

I wonder why isn't there a smart pointer which implements deep copy
semantics.

That would be helpful in following cases:

class X {
    ...
};

class Y {
    X * x;
   ...

public:
   const X * getX() const; // X may not always be present, so might
return NULL sometimes.
   ...
   Y(const Y & y); // I will have to implement deep copy semantics
here:-(
   Y & operator=(const Y & y); // I will have to implement deep copy
semantics here :-(
   ...
};

For such a case, I would love to have wrapped around my data member
pointer 'x' with some kind of smart ptr like "std::deep_ptr<X> x;" so
that I get the followng benefit:
1) I don't have to bother about manually implementing deep copy in
copy constructor and aissignment operator. And yes, all exception
safety things are also taken care of.
2) I will still continue to have the liberty that getX() may sometimes
return NULL i.e. X may not always be present as per the real world
object I am modelling.

The only way (I can think of) for achiving both these benefits
together is to implement a deep copy smart ptr and use it.

I could do that, but I was was wondering, if people felt the need for
all other kind of smart ptrs and put it in the standard/boost library,
why was this kind of a deep_ptr missing?

In other words, am i missing something? Or am i using C++ in a not so
well recommended way?

Thanks,
Arijit