You can get it fixed at any real bike shop, but it's probably cheaper to buy another cheap (or used) bike.
It's only a do-it-yourself job if you're kind of a backyard mechanic, and it can require special tools at that. Unless you have a free replacement part and know how, it's almost definitely cheaper to give it away to someone who can fix it themself and get another bike.
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You can get it fixed at any real bike shop, but it's probably cheaper to buy another cheap (or used) bike.
It's only a do-it-yourself job if you're kind of a backyard mechanic, and it can require special tools at that. Unless you have a free replacement part and know how, it's almost definitely cheaper to give it away to someone who can fix it themself and get another bike.