I have a couple-one came frome Office Depot and the other was bought at Staples after the first broke. Try office equipment stores and try them out. One plus is they do not get hot. That being said I like my loupes better for most work.
I used "loupes" as a generic term. Brownells has Optivisors. It is page 206 in Catlogue 56. Go to Brownells web site and type in Optivisor. http://www.brownells.com
Shop equipment and some hardware stores have them also. They have various magnification and focal lenghs. It is good to try them out if you can.
pricey but I like the Electrix Halogen and the Luxo. I do a lot of precision work where I work and these are both brands I have used. They last a long time if taken care of also cheaper ones cause fatigue eventually if you are working on something for 4-6 hours it pays for the quality.
I like lamps and lights that do not get hot. Hallogen lights are the hotest. I also like flourescent screw in lights - they do not get really hot as said above when I use my loupes and round flourescent light bulbs in my magnifier. You might visit a couple of machine shops and see what they use. That being said - Nice internet URL source above.
Some truth to the hot of the halagen, I work on really small stuff though (tiny electronics mostly) and the amount of light to me is most important, my eyes are getting old and working with parts that are .05 to .1 inches gets real hard without the "bright"
The Luxo lamps are flourescent, and Electrix makes them also.
Another very good system is the Vision Engineering Mantis but it is way too expensive for a home workshop.