You need the front panel. These are usually sold as a set of the front and back. When you do the replacement, make absolutely sure you transfer the translucent light guide (small piece of white plastic) and the adhesive speaker covers over. One good thing about this replacement is that you don’t have to remove the motherboard or even disconnect the joycon guide rails completely from the middle mounting panel. Take your time, and be very patient. This replacement means detaching the digitizer and screen.
If you can’t find the case here, you might be able to find it on Amazon.