https://www.gearslutz.com/board/all-things-technical/1283146-primo-em283-capsule-diy-fig-8-a.html
Wish I had more time to mess around with these kind of things.
hmmmm.....
a micro sized MS or Blumlein stereo mic....wouldn't be too hard. It's the housing that I'm wondering about for a coincident array like that.