So do you make your own powder? I've been looking into it online, no-one seems to sell it.I clear my wine with dried, powdered eggshell.
It takes about a month. But it works.
Mind you, I should note, it reduces acidity so you may need to add some back in to balance it once cleared.
If you do how do you go about it? We just put our shells out to deter slugs, rather make better use of them tbh