Add property to arbitrary java bean

I want to write a function that, given an arbitrary java bean as an argument, returns an object that is a copy of that bean but that belongs to an anonymous subclass of the bean's type that contains an additional property. Let me illustrate with an example of what I have so far:

Foo.java:

import lombok.Data;
import lombol.AllArgsConstructor;

@Data
@AllArgsConstructor
public class Foo {
    private String bar;
    private String baz;
}

Garply.java:

public class Garply {
    Foo fooWithQux(Foo foo, String quxVal) {
        return new Foo(foo.bar, foo.baz) {
            private String qux;

            public String getQux() {
                return quxVal;
            }
        };
    }
}

This seems silly because I can never actually call getQux(), but a tool I work with uses reflection to successfully find the qux property and do what I want with it.

My issue is that I don't want to have separate fooWithQux() functions for each type that I want to be able to add the qux property to. Ideally I'd have something like beanWithQux() that accepts objects of arbitrary type. I think I could make this work with something like the following:

public T beanWithQux<T>(T bean, String quxVal) {
    class BeanWithQux extends T {
        private String qux;

        BeanWithQux(T bean, String quxVal) {
            // Here's where I'd like to copy all of the properties
            // from the Bean into the BeanWithQux

            qux = quxVal;
        }

        public getQux() {
            return qux;
        }
    }

    return BeanWithQux(bean, quxVal);
}

Here's where I'm stuck. I don't know to copy all of the properties from the given object into my new object. Anyone have ideas? Ideally there would be something I could do using lombok (I control the Foo class and can add annotations like @Builder if need be) as opposed to writing a bunch of reflection magic myself.

Thanks!