looking for 100% dairy free kefir starter?

my son has an anaphylactic dairy allergy, but I want to start slowly incorporating kefir into his diet for gut health benefits. I'm interested in attempting homemade soy milk kefir, but I cannot find a brand of kefir starter (not culture obviously) that truly contains no milk.

with an anaphylactic allergy, I need a brand whose label does NOT say:

- may contain milk (or traces of)

-made in a facility that also handles milk

- contains skim milk to preserve grains (or any other milk obviously, I saw this on a few brands)

it has to be 100% dairy free.. any brands you have at home that don't have this?? I am striking out. thank you!!