Mind Sharpener

Source: Tasha’s Cauldron of Everything p. 22
The infused item can send a jolt to the wearer to refocus their mind. The item has 4 charges. When the wearer fails a Constitution saving throw to maintain concentration on a spell, the wearer can use its reaction to expend 1 of the item’s charges to succeed instead. The item regains 1d4 expended charges daily at dawn.