Ktm rectifier help?

Hi all, I’ve been looking for a rectifier to change current from ac to 12v dc to run led rear tail light on my ktm xc. I have bought two ‘ rectifiers’ so far but they haven’t worked. The current coming from stator is ac and I need dc... anybody know where I can find a reasonably priced rectifier? I’ll only rarely be using the light( only for time card events). Thanks!