This toilet paper extender will work for your toilet paper holders that look like this! It might also work for toilet paper holders that look different from this, but I haven't tested that.
You will need to print this model twice—once for each arm. But I recommend tuning your parameters and printing it once to verify that it works instead of printing both at once.
Unless your holder is the exact same size as mine, you will likely need to customize this model. I've provided a parameterized version in OpenSCAD format. There's a lot of parameters but the ones you will need to customize are the ones that relate to the measurements of your holder:
There's a number of other features you can toggle and adjust as well—observe the changes in the model as you adjust them and you'll probably figure out what they all do.
I somewhat suspect this will be the strongest orientation to print it, but I did not test extensively. If you disable flat edges, you will probably want to print it with the uninterrupted flat circle face down Let me know if you find other orientations work better! You will likely need supports regardless.
The author marked this model as their own original creation.