It's really hard to find a business idea.
Erm... actually - no. Go through your life open-mindedly and think about which problems are not yet solved or what's missing.
If you really, really can't come up with and idea of your own, ask other people. Place yourself into the city center for a day and ask everyone who's passing what he/she is missing in life or what problem they would like to have solved (the self esteem improvement is free).