Get yourself a Swiss ball
Swissball, exercise ball, gym ball, whatever you call it, they are a fantastic piece of equipment that is very reasonably priced.
They allow you to do strength work, particularly core exercise, balance work and even stretching.
There are plenty of videos and articles available to show you exactly how to use one.
If you don’t have any space at home, then check your gym or squash club. If they don’t have any, ask them to buy some.
One word of warning. At first, you can feel a little clumsy using one. It happens to us all. DO NOT LET THAT STOP YOU FROM USING ONE.
You will get better.
For around 10 Dollars, Pounds or Euros, it’s a worthwhile investment in your squash (or any other sport for that matter).