Failure.

Looks like dehydroretinol synthesized in a lab is way too fucking expensive.

And the only product so far I've found that has dehydroretinol without contamination from other forms of vitamin A (beta-carotene, Retinyl palmitate, etc) in them is some kind of make-up. And I'm not about to try to eat that.

I did find out that anhydrolutein converts into dehydroretinal in mamals, but searches for that were even more futile.

So, I've followed up every lead, scoured one end of the internet to the other, poured over research documents and this is all I came up with:

>Materials. 3-Dehydroretinal was prepared from the liver oil of the Indian freshwaterfish Wallago attu (Balasundaram, Cama, Sundaresan & Varma, 1956). The livers were homogenized in a Waring Blendor and extracted repeatedly with light petroleum (b.p. 40-60°)-ether mixture. The extract was dried over anhydrous Na2SO4, filtered and reduced in volume. The concentrate was kept at - 300 overnight and the precipitated sterols were removed by filtration at -30°. The filtrate after reduction in volume in vacuo was saponified with ethanolic KOH and oxidized over MnO2 (Camaet al. 1952a). 3-Dehydroretinal was separated by chromatography on a water-deactivated alumina column. The crystalline material obtained after four crystallizations had E1% 1431 at 385m,.u in light petroleum. Oral feeding. The compound was dissolved just before use in refined deodorized groundnut oil containing 50% (w/w) of a-tocopherol.

Tl;dr - It can't be done. At least, not by me.

Sorry /x/, I have failed.