The photo below shows the safety valve "saddle", as well as the tank filler caps (which were straightforward turnings from brass rod). The saddle was made in the same way as the new dome, with a thin flange squashed on to a rod. I soldered a spigot up inside it, and used this to hold the assembly while drilling out the three holes on the Proxxon milling machine. The front hole is for the whistle.

The two main valves (not sure of the right terminology!) were made from 0.8mm brass tube drilled out at the top to form a thin flange. They were then soldered in place.

The whistle was turned in the lathe from brass rod, although its extremely small size meant that it taxed my ability somewhat. On the second attempt I ended up with something that hopefully gives a reasonably impression from normal viewing distance:

Soldered in place: