Ready-made Cloud ERP System with Modern UI

I'm looking for a ready-made ERP cloud accounting system like onlineinvoices.com that offers these key features:
- Inventory Management
- Sales and Purchase Tracking
- Financial Reporting

I'm specifically seeking a system that has a:
- Modern and sleek design

I plan to integrate this ERP system with other software via API.

Ideal Skills and Experience:
- Experience with ERP cloud accounting system development
- Proficiency in UI/UX designing
- Proven ability in API integration with other tools
- Familiarity with inventory management, sales tracking, and financial reporting systems.

I want similar to https://www.onlineinvoices.com/