I usually go to the Maxiaids website to get stuff for my students. However, I just looked through there and didn't find much besides loupes that had a 20x magnification. I found some handhelds that went up to 16x, but that was about it. You may find something there though.

20x?!! Are you sure she's using a true 20x loupe? If you picked up a cheap loupe online, chances are, it's not a 20x. For instance: http://www.amazon.com/SE-Loupe-LED-Illuminated-21mm/dp/B0013E3DAG => advertised to be 20x, but turns out to be ~5.5x.

I would recommend first figuring out the minimum magnification power your wife needs to read small text. Reason: There is an inverse relationship between magnification power, and depth of field and field of view. Meaning, there is no 20x magnifier that can give you a huge field of view (I have a true 20x, and dear god, it is useless to me since it can only view about 1 character at a time).

Here's an example of the tradeoff: I own several Donegan OptiVISOR headband magnifiers. At first, I ordered their most powerful model, the 3.5x. The 3.5x has a focal length of 4", and a depth of field of about 1". This means, in order for me to have a clear image of what I'm observing, I need to make sure I maintain a 3" to 5" distance between the lens and the item under observation; it was just exhausting.

After trial and error, I ended up with the the 1.75x. It has a focal length of 14", and a depth of field of about 4". Which means, I can keep the item under observation at a distance of 10" - 18", which is much more forgiving.

In case you're interested in the headband magnifier: http://www.amazon.com/Donegan-OptiVisor-Headband-Magnifier-Magnification/dp/B0068OSIIS/