Don’t know about shops/retail, but they’re available with Cotic bikes as of now (stock arrived last week, and I’ve added them to the bike options).
http://www.cotic.co.uk/news/2017/manicnow
Paul and other riders at Cotic have been giving one a beating.
Only downside seems to be that the cable can become detached from the bottom of the post if you undo the seatpost clamp, slam the post in the frame, and then pull it out high again. Only something they discovered when quickly changing the setup for different height riders mid ride. Easy to prevent with a zip tie around the cable end (or not lending your bike to your mates).
Paul prefers the action of his to the Reverb he was using, so is sticking with the Manic.