Fortunately for you, no matter what decision you make, the problem isn't likely to recur THAT often. The Illithiad says that mind flayers can survive on one good meal a month, and I don't think Lords of Madness has stated otherwise. (Feel free to correct me on that, though, since I don't actually have the latter book). So unless you've got a seriously starving 'quid on your hands already, you've got some wiggle room to figure out what to do.
Illithids CAN rip out nonsentient brains, but the majority of their nutrition comes from the mind of their prey rather than just the grey matter itself, which is why they can't really scavenge. Dead food or animals will quell hunger pangs, but it really just masks starvation rather than preventing it, sort of like trying to fill up on bread and water.
I don't know about YOUR party, but mine seems to be a lot more forgiving and less disgusted by the brain-eating thing when it happens in combat. In an us-or-them life-or-death situation, killing the foe by any means you've got at your disposal is one of those things that just happens, and illithids tend to fight better with their natural weapons than with manufactured ones. There's a difference, somehow, between killing a person to eat them and killing them BY eating them, I guess, even if my own character doesn't quite see it that way.
Speaking from experience as one who's playing a friendly illithid themself, my reccomendation is to shortcut the problem via magic. Ring of Sustenance is ideal, if you've got funds and a chance to stop somewhere and buy one, and create food and water and your above-mentioned "not tasty" food sources can tide it over until you get one. Really, it's no different than what the rest of the party does- I don't imagine iron rations are exactly the height of cuisine. In any case, SOMEONE in the party ought to have prestidigitation if Glass doesn't itself, so the taste problem isn't really an issue unless you're hoarding cantrips.
My own Ikanthilossk counts its Ring of Sustenance as one of its two most precious possessions, though it only wears it around a single tentacle rather than all four at once. If your party is ever in Sigil, stop by the Brothel of Slaking Intellectual Lusts and say hi, okay?