Android developer needed to create app that will connect with our ERP system

We have an ERP system . We have a bussiness that sells build-it-yourself furniture. Our ERP's default app does not have the functionality we need.

    Our first project is to create an app that the order pickers can use. The order pickers are employees that go to the warehouse office, they receive a sales order and they proceed to collect the items in the warehouse based on that sales order sheet. When they are finished, they return to the warehouse office and give the sheets back and a warehouse office employee manually inserts the results into the system. We would like to stop using papers and have everything digitilized. The pickers will be given a tablet and a blutooth scanner and as they pick each item, they will scan it into the app and the app will send an api request to the ERP to update the picked quantity of that product. After they are finished picking the order, they will be able to confirm the shipment through the app.

The attached sheet has the specs for version one of the app. We need this project to be done very quickly. We would like to find a developer that can give us a flat rate for version 1 of the app. After version 1 is completed, there will be many more features we would like to add.