Igo-l for a 20mm diameter dripper, full stainless steel, double o-ring top..£15 delivered UK from ivapour-elixir. just bought one myself actually..
A7/SS Pheonix for a 14mm dripper, stainless steel, fully strip-able with bottom air feed and adjustable centre positive pin. again about £15 delivered from safer cigs (A7) or vapingthings ( SS pheonix )
It's excellent Karl, I've had a couple now . . . my first proper rebuildable, I found it a doddle to coil up ( which is saying something! ) as there's a nice bit of space to work in, whilst you're getting to grips with coil building.