I had the very same exact leak but on the drivers side. Very slow leak for over 6 months until it got worse and eventually pissed out any coolant in it. I was lucky enough to have a radiator shop replace the radiator for $189. It ended up being where the plastic meets the aluminum on the radiator right where it's crimped together. You can try some alumaseal from auto zone for 3-4 bucks. I used that stuff on my old truck when the radiator had the same exact leak and it didn't leak for years afterwards. Just make sure you drive around a bit after you put it in. It's a powdered type sealer. Never heard of it causing any issues in cooling systems. A mechanic of 40 years suggested it to me.