Where to buy a replacement for Apple Watch Ultra 2 Ocean Band Buckle?

The buckle for my AWU2 Ocean Band had fallen/ lost during hiking. Is there any suggestion or advice in which i could get a replacement for it? The straps are in great condition since this AWU2 still new. Realized that the buckle had been lost after finishing today session.

[Re-Titled by Moderator]

Original Title: Lost Apple Watch Ultra 2 Ocean Band Buckle