If you haven't done so already, you can purchase rack ears from your local Audient stockist where you brought your EVO 16 from.
You can find your local stockists here: https://evo.audio/where-to-buy/
Otherwise, if you're based within the UK, you can purchase these from our outlet store: https://reverb.com/uk/item/63295681-audient-evo-16-rack-ears-rack-ears-only