Technically this is not a magnifier but it makes their use far more effective if you read the post on using a magnifier you will have seen you need to hold the magnifier close. The correct distance means you have to hold the magnifier and book very close, but this is tiring. It is difficult to hold a book and magnifier for long periods.
The answer is a reading stand in some form. You can then move your magnifier over the book without having to hold it, it is also at a comfortable angle.
The construction of the stand is critical, if you go on-line you can buy stands for resting cookbooks on. These are fine for the purpose intended but they are not good for the partially sighted you need it to support quite a lot of weight. You will press on the page so the design has to be pretty robust. It also needs to have a variable angle for ease of use. If you are interested go to amazon reading stands .
If youare handy you can make one yourself.