Let me tell you a secret; chances are you'll never have the Right Idea. It won't show up on your doorstep, slap you in the face and give you its business card. If you don't have the Right Idea, make finding the Right Idea the first point on the agenda after you quit your nine-to-five job. If you look for it you'll find it. If that's too scary for you, maybe you don't want it bad enough. And honestly, that's perfectly OK as long as you can admit it to yourself.
In fact, the Right Idea is a myth. It doesn't exist. Once you expose it to the real world your Right Idea will change, get chewed up, spit out, change again, transform into a pupa and go through a metamorphosis before it emerges a butterfly (even then it might get eaten by a bird or lizard). It's all part of the process.
The wonderful thing is, you don't need to wait for the Right Idea. Just go. Do your thing. Jump and the parachute will appear.