You should still be within the warranty period. The answer to your question I think is yes, you can replace the 510 pin, but I would have no idea where to direct you.
I'd warranty it though if it's brand new. I mean, yeah, just the pin could have been faulty, but there could be something else going on with the tank to cause the pin to break. If they tell you not to send it back when you warranty it, try a new pin then, would be my personal advice.
Sorry to hear this happened.
Anna