Aventon Pace 500/350 Battery receiver, tray, locking cylinder and key assembly
This item can be used to repair a Pace 350 or 500 series ebike if the original factory keys are lost.
It includes the battery receiver and tray, plus a new locking cylinder assembly and matching key.
To remove the old assembly and install a replacement, the battery must first be removed from the bike. If you can't remove the battery because the key has been misplaced and the battery is locked on the bike, it must be removed first, perhaps with the assistance of a locksmith.
Installing the replacement parts requires some ebike expertise; while DIY is possible it's likely a job for an Aventon ebike dealer bike shop.