I have the same problem. There are soap making instructions on google. You might add the ingredients to that. I often use essential oils and use it before, or even after, my shower. Kind of gives me the same effects.
Days I can not use the bathtub I use herbal infusions/herbal teas in the shower. Put it in a plastic jug/plastic bottle and slowly pour it over yourself. Another way is doing foot baths in a square plastic pail where both feet fit comfortably. Or a bowl to do handbaths.