Konbucha/Kobucha (昆布茶) is NOT Kombucha, a fermented drink. Konbu-cha is from Konbu/kombu seaweed and it is full of konbu glutamine and asparagine umami deliciousness. We drink it as a tea, therefore it’s called konbu-cha (tea), but we also use it as a flavoring for cooking. I use this brand and it’s usually located at the tea section in a Japanese supermarket.
Substitution: If you can’t find this, you can substitute it with salt. However you will be missing nice umami from konbu.