I've got a pukka Donegan Optivisor with a 3x lens plate and I can totally recommend it. I've tried reading glasses and cheaper headband magnifiers but they're not anywhere near as good.
It's really all down to the quality of the lenses, and with magnifiers I've found you get what you pay for Darrell.
Front Rank used to sell them, well that's where I got mine, it was a few years ago though.