Found a website that let you choose a model and store to receive email notification when it becomes available, only available in US and Canada though.
iPhone Inventory Checker | Real-Time Apple Store Stock Alerts & Availability Tracker
Find iPhone 16 series availability in real-time across Apple Stores worldwide. Get instant email alerts when your desired iPhone model is back in stock. Track inventory across 18+ countries including US, UK, Canada, and more.
iphoneinventorychecker.com