Gateway Transaction ID Cloaking

I need a clean, reliable way to stop real transaction identifiers from ever reaching the customer side of my checkout flow. The top priority is PayPal: every PayPal Transaction ID must be swapped for an internal token before it appears in a browser response, confirmation email, or third-party script... (Budget: £20 - £250 GBP, Jobs: API Development, JavaScript, Payment Gateway Integration, PayPal, PayPal API, PHP, Software Architecture, Software Development)