Bought my EVO 16 secondhand - Audient has it so that if you register your product online they'll send you these rack ears for free. However, the person I bought it from had already registered the serial #, so I was unable to get the ears - and frankly, Audient customer service was pretty useless. After a week, they asked me where I was located and then never contacted me again.
So since it's impossible to find these in my country (Canada) I ordered from here instead. They arrived very quickly and they're well built. They attach to the interface via four screws so they're unlikely to fail, but... seriously, Audient, 2.0mm hex screws??? Every other screw on the unit is a Phillips head but for some reason they decided to use a different head for these mounting screws. Better hope you've got a small hex driver sitting around because they don't include anything like an allen key, either.