Full Website Quality & Security Audit

I run an online store that processes payments directly on-site and I’d like a fresh, expert set of eyes on every corner of it. I’m concerned not only about obvious vulnerabilities—SQL injection, XSS, CSRF,... (Budget: ₹1500 - ₹12500 INR, Jobs: Conversion Rate Optimization, Internet Security, MySQL, PHP, Security Auditing, User Experience Research, Web Security, Website Audit)