Those leak repair in the bottle elixirs are for the crooks who need to get rid of a car with a leaky radiator. They usually last just long enough that the guy who put it in to sell you the vehicle can say "geez, it didn't leak when you bought it".
There are a lot of good used radiators on the market. I would get one and do it right. With the radiator off, you can check the engine temperature sensor, clean it's terminals, and replace the fuel line to the pressure regulator. I realize it's not a 20 minute job, but if you keep the bike, it's a job your going to be doing, probably during the best part of the riding season. If you're lucky, it won't fail 50 miles from home.
Personally, I would replace it as a winter project.