Making bowl heaters is fun, but getting small heat resistant domes that are shaped like a parabola are difficult. Most small dishes and bowls are flat bottomed, and small round-bottomed woks are too heavy. However, by chance I stumbled on a good source - old stainless pan lids. Usually the lid handle screws off leaving a welded stud, which can be used to secure the dome to a spare home-made 'leg'. Normal brazed guard, and dredger lid (@BigScott ) fitted into the top of the dome.