Why can't I purchase a separate charging case?
Both units and charging case require unique connection settings that can only be set at a Sony Authorized Service Center.
When you lost, or have damaged your charging case or earbuds, you can send in the remaining headset unit(s) and/or charging case for repair.
Because of this unique tag-writing, the charging case and single units of the headset are not sold separately.
Authorised Service Center
Please contact Sony Authorised Service Center: once they receive your remaining headset unit(s) and/or charging case, they can replace your missing charging case or earbud and synchronise it with your original product.
NOTE: The warranty doesn't cover the cost of replacing the missing items.