I consider daily shower cleaners to be one of the greatest inventions of the past ten years. No way do I want to go back to scrubbing the shower every week. The down side of buying the product is that I haven't been able to find refills for any brand except Method which stinks, I mean smells, like ylang ylang. It takes quite a bit of it to keep the lime deposits from our water from building up quickly so we were throwing several plastic bottles a month into the recycle bin, sprayer and all.
I have made several attempts to come up with a formula that works, including several containing vinegar (stinky and mildew started growing). None of them worked at all. Research told me that the shower spray products work partially because they contain a sheeting compound. I looked online and could find not source for such a thing. Finally, I found the answer: Jetdry....the stuff you put in the dishwasher to keep the dishes from having hard water spots on them.
I mixed up the following formula which has been working well for about ten days:
Stir 3 tablespoons each borax and washing soda into enough hot water to dissolve them.
Add 3 tablespoons Jetdry (or whatever brand you have on hand)
Pour the mixture into a 32 ounce spray bottle then very slowly fill the bottle with water.
(If you fill it too fast, it will foam up.)
I use the bottle I had left from the last shower cleaner I bought. That way, I know what is in the bottle and don't have to label it.