Cant email support since I cant find my serial number

Bought the Iskur Genshin chair a few years back and it has now developed a crazy amount of wobble to the point where I slowly slide off the chair in its default position. Support pages show where to find the serial number on the chair but I cant find it anywhere after looking for 30min+. Just trying to find a way to email them about this when i don't have my serial number. Thanks