Cesar Cui's fairytale opera for children
Ivan the Simpleton ("
Ivanushka-Durachok") has just been released by Aquarius-Classics. It is actually a recording from 1949 though I presume it has not previously been released. You have to buy directly from Aquarius, via messaging them (address on the website) and then paying by paypal. I've just ordered mine, $13 including postage (I've bought from them before with no issues).
http://aquarius-classic.ru/album?aid=387&tid=7&ver=eng(This recording was previously mentioned here -
http://artmusic.smfforfree.com/index.php/topic,6362.0.html )
Synopsis and history of the opera here -
https://en.wikipedia.org/wiki/Ivan_the_Fool_(opera)