Well i spin my Hs50s to pretty high RPMs and the stock black plastic 3 pin plug has been absolutely fine. It is designed to handle the load of the system.
If you want it to be weather/water resistant, you could look into weatherpack connectors.
As the engine spins higher, the voltage increases but i think the amperage stays the same?
The Tecumseh Service Manual has a handy chart-
If you are worried about the amperage, you could always add an inline fuse but i have never needed one. I am running headlight, taillight and brake lights on the same system.
Black widow used to sell the connectors, not sure if they still do. I have purchased them from ebay before, they turn up sometimes.