Talk to people outside tech. Lots of small problems worth solving, but not in tech. Also, just because it's a problem in someone's day to day won't mean they'll pay to fix it.

Good luck!

"just because it's a problem in someone's day to day won't mean they'll pay to fix it."

The best way to measure is that they've hacked a solution themselves using inferior tools. This is where the 10x recommendation comes to mind - you can do it cheaper, faster, better.