I recently found out you can get foaming soap refills as tablets. I hadn't previously found a way to refill hand soap pump style dispensers without more plastic. These are from Meliora.
Thanks for sharing how you do it, that also sounds like a good deal.
I've been doing something similar, where I bought unscented soap refills and add some essentials oils to add a scent that others in the house prefer.
There is a little bit of adjustment to get the ratio right and but I just leave a little headspace so I can dilute down with water to the right consistency.