Flutter Developer for Ride-Hailing App Customization

I am looking for an experienced Flutter developer who already has a ready-made ride-hailing/taxi source code or has previously developed an application similar to DiDi, DiDi Flex, or InDrive. IMPORTANT: I do NOT want to build the entire application from scratch... (Budget: $250 - $750 USD, Jobs: App Development, Database Management, Flutter, Mobile App Development, Mobile Development, Node.js, REST API, Software Development, User Experience Research, User Interface / IA)