I'm speaking from first-hand experience... just carry the shit on the plane with you inside your jacket. It's a small metal crimped cap, not a fucking 12" blade for fuck sake. Yes, the detector will go off, and it will go off for the bottons on your shirt, the zipper on your jacket, the buckle on your belt, etc. Airports DO realize these SMALL TINY metallic objects have no big concerns, just like your SMALL TINY cap on your Winny won't be a huge concern either. Trust me, as long as you don't sweat bullets and look suspicious as hell (like you're packing a fucking sawed-off shotgun), then they won't ask too many questions, or rip you apart, literally. Just keep your cool!!
Syringes here in Canada can be bought by the hundreds. Walk into a pharmacy, ANY old pharmacy, ask for the size, and they'll give it to you. No questions asked!! I have never ordered a single pin from the internet. There is no needle-exchange program here like there is in the States. It's none of their fucking business what I'm using it for anyway. And if they are reluctant, then I become a prick and tell them that I'll just have to share my needles with my friends. TRUST ME, they'll be more than happy to sell it to you then. Good luck.