yo can get good metal flip up sights from Amazon for $2o or less
https://www.amazon.com/Trinity-Forc...qid=1515613454&sr=1-8&keywords=flip+up+sights
or
https://www.amazon.com/Upgrade-Feya...qid=1515613529&sr=1-9&keywords=flip+up+sights
https://www.amazon.com/Trinity-Forc...qid=1515613454&sr=1-8&keywords=flip+up+sights
or
https://www.amazon.com/Upgrade-Feya...qid=1515613529&sr=1-9&keywords=flip+up+sights