Well, I decided to bite the bullet and order the Pentax 3.5mm. US $243 shipped, snap up this deal while it lasts, last eyepiece in stock too. Don't have much to lose I figure. Ain't gonna come across any reasonably price Ethos or Delos any time soon it seems.
You will be very happy with your new eyepiece and in the process saved a lot of $$$$ over some of the other options.
Cheers