AMVR Controller Grips Compatible with Meta/Oculus Quest 3/Quest 3S, Silicone Accessories Non-Slip Handle Cover, Adjustable Soft Hand Strap Fits Small and Medium Hands (Not Fit Official Charging Dock Battery)

There is no fix that is going to make that work again. You can find replacement battery doors online, specifically controller straps like this If your interested and in the US I can also send you a new one since I lave multiple. Really your better off investing in those straps.