Then, the lumiloupe, a maglight with attached loupe of good quality,
might serve you well. The triple lens is intended for the inspection
of diamonds originally. The quality necessary comes at a price.
But now plastic lens are of good quality. It’s a special order to get
glass lens for glasses; they are usually plastic. Radio Shack sells a
set of three plastic loupes of varying powers which are very good.
And the diameter is about 25 mm; giving a broader field of view.
Another suggestion might be a monocle loupe attached to a hand band
which would leave a hand free for a light. Of course if you set
stones more frequently there’s nothing like a microscope.