Good question. This report from December 2020 is that it will be available, not that it actually is available. Tesla announces new CCS charging adapter but North America launch still unclear - ElectrekIs the official Tesla CCS adapter from Korea actually available? I had heard that it was being offered/promised by Tesla, but haven't seen any reports about it since.
A post on this page in August 2020 quotes @MarcoRP as saying it is undergoing testing in South Korea CCS adapter being tested in South Korea!
And more discussion here Tesla Announces CCS1 Adapter Coming to S. Korea Early 2021