If the new bottle is pretty small there is a possibility that it might have just overflowed the new bottle once it got real warm and full. Where does it overflow to? Could be you are just seeing the remnants of that?
Years back I crushed my stock right radiator so I sent it off to Myler's Radiators in Utah. He straightened it out, fixed the leak it had and sent it back for WAY less than the price of a replacement...I think it was like 55 bucks or so back then.....might be more now....and it only took him about a week and half to get it back to me!
I also had a stick get flipped up once and it jacked the front end skyward as it ripped the left lower hose connection clean off the lower tank. I patched that one with epoxy to make it back to the trucks as we were about 15 miles back in the woods. It did leak some of the Tang mixture I used to refill it as that is what I had in my camelback, but it did make it back to the truck under its own power. I was glad I had started carrying a couple small packs of epoxy with me after I trashed the first radiator when this incident happened! I ALWAYS carry a couple small packs of epoxy with me now...on EVERY ride!
Myler's also fixed that radiator for me!
I then started watching e-bay and picked up a spare for both sides from bikes getting parted out for about 50-75 bucks each. I figure having a spare is real good insurance.
Most of those Chinese
ones look good (in pictures anyway) but are thicker than stock so you loose room which I need since I added a cooling
fan. Never do think I would trust them all that much either as Chinese aluminum is not near the quality of US and Japanese aluminums...in my experience anyway. So for me I want to stay with genuine Yamaha