Qt LNK2019 issue with custom QVector class

Question

I have a custom QVector class, which has a single function: to return the element of the vector fulfilling some conditions.

Here is some code: customvector.h

#ifndef CUSTOMVECTOR_H
#define CUSTOMVECTOR_H

#include "customfile.h"

#include <QVector>

template<typename T>
class CustomVector : public QVector<T>
{
public:
    using QVector<T>::QVector;

    CustomFile find(int index);
};

customvector.cpp

#include "customvector.h"

template <typename T>
CustomFile CustomVector<T>::find(int index)
{
    // Processing
}


#endif // CUSTOMVECTOR_H

The code driving this:

CustomVector<CustomFile> files;
files[0] = CustomFile(0);
files[1] = CustomFile(1);
qDebug() << files.get(0).index;

customfile.h

class CustomFile
{
public:
    CustomFile(int index);
    int index;
};

customfile.cpp

CustomFile::CustomFile(int index)
{
    this->index = index;
};

The issue I am having is that I keep getting a LNK2019 error, telling me that the find(int) function is an unresolved external symbol. Can anyone help?