If that is the screw, it does not look stripped to me. If it isn't holding it is likely the nut. But since the screw isn't stripped, the nut is probably not stripped either. It is probably a nut insert and may be loose in the plastic.
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If that isn't the "stripped" screw, you might try looking at ACE hardware. They usually have a good assortment. It is also likely a metric screw.
If that is the screw, it does not look stripped to me. If it isn't holding it is likely the nut. But since the screw isn't stripped, the nut is probably not stripped either. It is probably a nut insert and may be loose in the plastic.