Here’s an idea: find “someone else” with a problem and work on that. This works especially well if the someone else is in business, very busy, and has some money. Chances are better that your solution to their problem won’t have much competition: if it did, they would have already gone with it.
I know this is the opposite of “scratch your own itch”, but I always found that advice overrated. I have always been much more successful scratching other people’s itches.