I'm sceptical of the claim that they couldn't eliminate the majority of them from stuff that's shipped up to the ISS. Even if it meant making special space certified hair conditioner.
I don't see why not either, just get "organic"/plant or mineral based cosmetics, deodorants and hair products.
There's a nice paper on this, ICES-2018-123 "Dimethylsilanediol (DMSD) Source Assessment and Mitigation on ISS: Estimated Contributions from Personal Hygiene Products Containing Volatile Methyl Siloxanes (VMS)". The upshot is more than half of the siloxane burden on ISS comes from God knows where (packaging, plastics, machinery, you name it).
https://ttu-ir.tdl.org/items/ff1a240e-1fb1-4b04-acb2-42e9c45...