I have looked through the repositories and can only see two screen magnifier packages,
1. xzoom This is the simplest one I can see and it works on my machine
2. kmag This is designed for KDE desktop really and will install a lot of other packages (dependencies) when it installs.
They both seem to work in a similar fashion, and will open a window for you to see the zoomed screen area, kmag has the option to follow your mouse as it moves which would probably be more desirable. You can install either (or both) using synaptic package manager, of from the command line with...
sudo apt-get install xzoom
for zxoom, and...
sudo apt-get install kmag
Once installed you can start them from a terminal window, or check in the menu for an option, on my LXQT installation they are under Universal Access
and are "kmag" and "Screen Magnifier"
Once you have them installed and you get them working I can advise you on setting up a key combination to start them.
If there is anything you are unsure of please feel free to ask, I was new to this once and know how difficult some things can be to start with