laredo

Hello guys, I have a problem. I recently flushed the radiator on my 02 Grand Cherokee Laredo V8. The drain plug on the bottom would'nt turn by hand so like a big dumb animal I used pliers to turn it. Well it seems i've broken it, leaks no matter how much I play with it. It's a slow leak but I have to add coolant every two weeks or so. My problem is I cant find a replacement valve anywhere, its just a cheap plastic valve. Is there a way to replace it or plug it or am I screwed buying a new radiator? Any info would be greatly appreciated.
Thanks
John