I have long looked for the refill bags of shampoo that are available commercially (eg for salons) but I haven't found them to be able to purchase (for me ;-) I can barely find them for hand soap (I use bars in the bathrooms but prefer liquid in the kitchen - but also would prefer not to keep buying the bottles - esp because the pumps cannot be recycled)

Fashionista editor buys from March listed a bar shampoo brand I hadn't heard of before - Nole (there should be an accent aigu on that last e but I can only do that on my phone ;-)
https://fashionista.com/2022/03/fash...cts-march-2022
https://nolecare.com/products/bundle...oner-horsetail