We don't offer replacement keys at this time, but they are generically available Reention keys, made be Reention. There are a few 3rd party websites that offer replacement Reention keys for Reention battery systems. Here is one of the popular choices for ordering replacement keys:  https://flx.bike/products/keys

Choose the "attack" option and message them the 3-digit lock cylinder number in order notes  to get those keys. 

They do not need to know what brand bike you have, as long as you are ordering keys from a Reention supplier.

Lock cylinder number location is shown below: