If your radiator is brand new then you should not need a receipt, go back from where you bought it and explain the problem, they may even have spares lying around because many radiator manufacturers supply merchants with spares in case the radiator may have been supplied with parts missing. It happens quite a lot. If this does not appeal, then if leaking from a thread wrap p.t.f.e. tape around the thread and reseat.
DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!