Since most of us don’t have MLB money to have a number of backup gloves at the ready, a broken string in the middle of the game is bad news. I carry a kit in my bag in case I have to make a quick repair and just have a kit like below:
You can buy the needle and 2 leather laces on Amazon for around $15.99
However, for bigger jobs, or complete restrings, I’ve always found it frustrating and easy to screw up taking your glove out of service. In the Evansville area, I’ve always sent players to some local places that do it for you at a fairly cheap price and a quick turn around time normally.