Hi BK
I've made small globe valves for LC Masons Mini traction engine, there are a few designs about if you look at LBSC loco plans you will find a drawing, if your stuck I'll post a Crap O Cad drawing for you here.
There quite simple to make straight forward turning job the hardest part is silver soldering it together as you can clog up the works if you use too much solder.
Hope this helps
Stew