I don't know about second hand, but coincidentally I was just looking at parts on eBay and there's new ones on there for around £60. I don't know what the qualities like though.
Leaking from where, can you see the exact spot?
...I was looking at these https://www.ebay.ie/itm/Aluminium-Racing-Radiator-for-Yamaha-FZS600-Fazer-1998-2003-Engine-2002-2001/253252829705?hash=item3af70b8209:g:dZQAAOSwY~1aIPjT#shpCntId anyone has used these before.Also yesterday i was removing the old rad and one of the nuts that holds the rad fan were locked and i had to use extra force to get it out after hitting it up. When i took the rad off the fan blades came off the fan. I am not sure if this was just sitting there - which i dont think so or it was glued. I tried to put it back but i don't seem to figure out how did it came out...