ALUMINASEAL or Bars leak for aluminum. Best isea is replace the radiator.... Never mind you have a plastic radiator. maybe JB Weld, but Id just make the leak worse so they have to fix it. Not recommending just stating what I would do.
I have this same type of leak. I am being told that it is the radiator. I am having it replaced Ina couple days and I'll get back to you guys. I really hope this fixes the issue.
Mine is leaking a little more that than yours I believe.