Hello Nelson,
Yes, Asus strix 3090 water block is compatible with ASUS strix 3080.
Here is the link to our water block BP-VG3090AST.
When you log in, you can purchase.
Any more questions, feel free to contact us.
https://shop.bitspower.com/index.php?route=product/product&product_id=7913&search=3090ast