A month ago, Crinacle sent me a link to a new item that showed up on the Sounds Good Store on Ali Express -- the long awaited cheap Ear & Cheeks Simulator modeled after the GRAS 43AG. I quickly added it to cart and it arrived this weekend!
This is basically an artificial ear and mounting plate that attaches to the coupler that I already have been using for a while now. This allows for more accurate headphones measurements and it can still be used for IEMs and Ear Buds if needed. I've already tested it on IEMs with and without the ear plate, and they measure the same, so that's good news as well!
Here's some measurements I already took from this unit...
AKG N700NC MK2