This thread may sound silly, but there's some truth here. Time you spend waiting for the idea is time you waste actually implementing an idea. PMF doesn't happen in your head, it happens when interacting with the market. Get something together, pitch it, refine it, repeat. You'll get there.

I would suggest starting the "idea" with data about paying customers. There's a lot of data out there. Find a market, figure out what they need/want and build a POC. Figure out if your market will pay for it and garner feedback. You might just find that your market will reveal the elusive "idea" for you.