The Suzuki part number is
74120-64A00.
There are several online genuine parts importers that could get the part for you. One of those is Amayama, they list it for about AU$300, plus post.
https://www.amayama.com/en/part/suzuki/7412064a00For that sort of money (yes, it will be brand new), I would be considering taking the old core to a radiator specialist and see if they can solder up the leak.