Most top online sportsbook brands offer in-game wagering. Books like PointsBet, Caesars Sportsbook, DraftKings Sportsbook, FanDuel Sportsbook, and BetMGM offer in-game odds in games across many sports.
Look for a tab labeled "Live" or "In-Game" at your mobile sports betting app of choice to filter for in-play wagers available at a given time. Live betting sites (online gambling sites) are generally the exclusive home of in-game betting, as the changing odds and computer algorithms related to live betting function much better at online sportsbooks, compared to live sportsbooks.