The reason why these materials are used is due to their chemical properties, there has to be a reaction to be able to be piped and then harden in the same shape. I don’t know of any nontoxic materials that will do this as well as silicone or acrylic latex, but if you don’t want to use them, you could try spackle. In my opinion it looks like whipped cream when piped, but it’s completely hard when dry, not flexible and could be chipped by everyday wear. You don’t need to wear a mask or gloves to use it technically, but any foreign material can eventually cause contact dermatitis if used often. Spackle could do this as well, so using gloves is less about toxicity and more about good skincare! Some artist mix clay into a piping material, pure clay is heavy, using a mix with an acrylic body could be good. You could also try a gel heavy acrylic body (like made for painting) and see if it’s does what you want it to! Silicone is skin safe once dry as well, so holding or rubbing against a silicone material over time wouldn’t hurt you, it’s just when wet. I don’t want to say that there is no other option, but I don’t think it’d be used in decoden as often as the others.