If you watch this [guide|102598|video] and skip to 3:25 you will see how to remove the front facing camera. Looking at it briefly, it seems to be do-able. The camera seems to be very, very cheap from this link [https://www.witrigs.com/oem-front-camera-for-xiaomi-mi-mix-2|here] (currently out of stock) or on eBay [https://www.ebay.co.uk/itm/OEM-Front-Facing-Camera-Module-for-Xiaomi-Mi-Mix-2/113725830262?hash=item1a7a967476:g:1ZAAAOSwDudcvYvD&frceupt=true|here]. I hope this helps.