Hi Guy
I doubt that PTFE would last very long as the hot air would erode it.
I have been told that you can buy 4mm OD microbore brass pipe on the bay, this could be cut to length and worked in an electric drill to size it.
I normally form the chamfered lead in by simply spinning the brass sleeve up and putting a Stanly knife blade up it --- works well.
I wonder if the leaking Hawks could be sorted the same way as I did my HW35, with a little loctite 271 forced into the joint from inside the cylinder ?
All the best Mick