Itch only has the demo, correct.
For a DRM-free copy, the highest tier on Patreon gives you access to individual builds of the game at the moment (as long as your pledge is active): https://www.patreon.com/collection/380513?view=expanded
You could also buy the game through my online store at https://retronator.com/store (if you can fight your way through the text adventure interface), which includes the Steam Key for Learn Mode, but if you write me to hi@retronator.com after purchase I'll send you a dropbox link where I upload all the builds, so you can keep access to all future releases as well.