A lot of people think gaining an attestation means airlines will hire them. This is not the case. Just because you have an attestation does not mean you will have guaranteed employment, in fact many people attend assessment days and still fail. Paying to gain an attestation will not make an airline favour you more over someone else. I would say if you want to gain an attestation, complete a training course with an airline.
If you still wish to do so, SkyPeople offer training courses for attestations.