Busy Accounting software Add on

I need an add-on for Busy accounting software that integrates with an external API. Prefer someone from Delhi NCR Region in india

Key Requirements:
- Billfree menu item in Busy
- Login form with username/password
- API call on form submission to store response auth token
- During invoice creation:
- Button/shortcut to hit API with above auth token and load response into iframe
- Return hidden variable data to Busy on iframe close
- On invoice save, hit API with bill-level data and binary PDF copy of the bill and data in JSON format

Ideal Skills:
- Experience with Busy accounting software
- Strong knowledge of REST APIs
- Proficient in JSON data handling
- Frontend development for iframe integration
- .net project