If you don't _____ for playing games or taking part in Athletics, you may wake up early in the morning and run for a kilometer in the open air.
If you don't _____ for playing games or taking part in Athletics, you may wake up early in the morning and run for a kilometer in the open air.
Explanation
"If you don't find opportunities" fits grammatically and contextually — it refers to lacking chances to play or participate.
The sentence then suggests an alternative way to stay active.