I think there's just a spelling problem.
The correct structure includes had: I'd better go now. You'd better hurry. However, we often don't pronounce the 'd - as we don't pronounce t or d in many other cases:
mustn't, I can't bear/stand/go..., mind the gap, etc.
Sometime you can really hear that slight difference between I'd better and I better but it's such a small thing that it can easily get lost. Still, it shouldn't be left out in writing