Pimpl idiom with inheritance

I want to use pimpl idiom with inheritance.

Here is the base public class and its implementation class:

class A
{
    public:
      A(){pAImpl = new AImpl;};
      void foo(){pAImpl->foo();};
    private:
      AImpl* pAImpl;  
};
class AImpl
{
    public:
      void foo(){/*do something*/};
};

And I want to be able to create the derived public class with its implementation class:

class B : public A
{
    public:
      void bar(){pAImpl->bar();};    // Can't do! pAimpl is A's private.
};        

class BImpl : public AImpl
{
    public:
      void bar(){/*do something else*/};
};

But I can't use pAimpl in B because it is A's private.

So I see some ways to solve it:

1. Create BImpl* pBImpl member in B, and pass it to A with additional A constructor, A(AImpl*).
2. Change pAImpl to be protected (or add a Get function), and use it in B.
3. B shouldn't inherit from A. Create BImpl* pBImpl member in B, and create foo() and bar() in B, that will use pBImpl.
4. Any other way?

What should I choose?