I live in a state that (mostly) requires that you buy beer by the case. I feel your pain. ("Mostly": there's still the bar option, and there are a very few places where you can buy mixed cases or six-packs of things other than the big mainstream beers.)
The solution I'm partial to is the beer co-op. Mine started as a group of coworkers; we've scattered to a bunch of different companies by now, but the co-op remains. Every 4-6 weeks the organizer sends out email announcing a planned buy, with the goal of getting a multiple of 8 people (12 works, but we prefer 8). Participants get a case with variety of beers and divide the total cost. I've gotten to sample some beers I'd never have tried (or known about) otherwise. (Most people don't participate every time, but the organizer does because, hey, beer.)
If you're doing a co-op anyway, then it's easy to add on the occasional "side buy" -- something that comes in 25oz bottles, or is particularly expensive, etc. So long as there's enough interest to get the case, people can then buy them individually.
You can be very organized about this, requiring commitments in advance, or you can be flexible and deal with the occasional surplus. People interested enough to organize co-ops usually don't mind some surplus (assuming finances aren't too tight).