Natural wick?! Please share more, I would be interested what you ended up buying as I will be ordering a Cobra and venturing into buildables very soon...
Either 100% natural cotton twine, cheese cloth, teabag string, 100% natural hemp twine will all work. Cheese cloth and teabag string are ready to use where both twines should have 3 separate 20 minute boils, draining and replacing the water each time. I then leave in the oven on" warm" setting overnight(170°f) to dry and prevent any mold growth.
Bought the 1mm hemp twine natural color I'm using now from lovepedal on eBay. Great seller. I'm using it in my AGA-T2(3 pieces) and all my EVOD( can't recommend this clearomizer enough,2 pieces) heads.
Does it wick as well as silica? No nothing does. Can you dry burn like stainless and silica? obviously not. It takes a little more care and time but, is worth piece of mind. Though I think there's nothing solid saying silica and oxidized stainless is truly unsafe why chance it? There are options.
You still need to tip the AGA T like ss mesh but, it works flawlessly in EVOD heads. Had the t3s and they stunk. The changes in the EVOD you don't get the gurgling and great vapor and taste. Just have to give a new wick a tiny bit more time to do its thing.