I wouldn't suggest ANY conductive metal by virtue of the fact that a little spark could very well ignite your leaking pipe bomb (which it might as well be).
All you need is the PVC (a foot or longer), duct or electrical tape, large bottles of a quality butane and two cheap 'knock out' end caps. Any hardware store that sells plumbing supplies will sell the PVC and the ends; NOT large bulky PVC caps (although those could be used with a bit more work), the ones I am talking about are small, cheap, 'knock out plugs'- they fit right inside the PVC to cap it.
You take your knock out caps. You poke or drill several small holes in it, this cap goes on the end of the PVC that the butane flows out of (the bottom). The other cap you poke one simple small hole in the middle, which is where the nozzle goes. The nozzle that will allow you to fill the pipe with butane actually comes with the butane. On the butane bottle there is usually a cap (typically red) with all those little plastic pieces that you can knock out. They vary in size, you should easily find one that fits perfectly in your little hole (hehe). And you want it to fit tight, so that gas can't escape.
Push your nozzled cap in the PVC and use duct or electrical tap to tape it (the cap) down and seal it up. I suppose you could also just super glue it or something. The other end, which will be the bottom, you want to leave so that you can remove the cap to fill it with herb and stuff; you want butane to flow easily from there anyways. You don't want the holes too big or herbal material could escape, but it helps anyways to just fasten a coffee filter or something there with an elastic band.
Be very careful when messing with the butane; discharge yourself on something (static electricity) before you start to fill the pipe up, don't smoke, don't have any other open flames or heat source, don't be stupid. Do this outside or where it is very well ventilated.