Write an email to HR, leaving a paper trail in case they retaliate...
If they don't solve this issue, I would just go home to take a dump and come back without clocking out... If they complain, I would tell them they need reasonable toilet paper.
You might get fired for it, so I would start applying for other jobs before attempting this.
2 hours? As a non-american, I sometimes forget how car-centric and spread out American cities are... I knew Americans drive a lot, but 2 hours? Please tell me that's the combined back and forth trip, not each way...
As someone with digestive issues, I would approach HR about this saying I need an accommodation under the ADA, with said accommodation being reasonably high quality toilet paper.