Flutter Mobile app development

We are looking to get a flutter based Mobile App developed. This application is a map based application. To find pointers on the map and interact with it. High importance to modular & well designed code which can be reused. All the required APIs for the above features are ready & available. Backend Development not needed except for a small backend service to store user preference information. Wireframe not created. Looking for suggestions on design. Can provide examples of similar applications.

The following is the overview of some of the requirements:
- A map containing custom icons to identify pointers on map, including fliter icons & filter conditions, search feature, custom styled look for two different themes.
- Stripe Payment gateway use in the app, including UPI
- Internationalization; with ability to add new lanagues later. In-app support needed, no API available, Two themes; dark & light.
- Modularized & extensible code design with source code to be made available
- Android & iOS support with app upload
- minimalistic UI/UX design (not material design instead custom design)
- support for different mobile screen sizes
- splash screen

Detailed Feature Requirement document will be provided after shortlisting the candidates. Reach out to us for any questions.