Update: added Fusion 360 source file, to make easier remixes and tweaks.
There are several Y motor adapters, but some of them not rigid enough, others consists of multiple parts. I designed one that is realy strong and prints as one peace. It should fit press fit pullye and adjustable one.
I have used dumpers from this lot https://goo.gl/RaR1gT.
Orientation is shown on the picture. Supports are needed only from build plate.