If the halogen has a shaped reflective upper area, a dome is unnecessary and will achieve nothing , all you need is a ceramic fitting rated about 300W and a wire light cage to stop the reptile from touching the very hot globe surfaces and very hot ceramic fitting.
Please don't mount a dome fitting with halogen on top an plastic mesh lid , that's a recipy for a disaster.
If you must use a mesh lid , then you are better off mounting using a lamp stand that's adjustable in height.