Recent research on muscle glycogen replacement indicates an optimum ratio of 4:1 carbs to protein, rather than 2:1, although the research seems to be focused on endurance exercise. The link below discusses this and has other links to research:
Nestle sells a flavored reduced fat milk product in 16 oz. (200 cal, 8 grams protein) and 32 oz. (400 cal, 16 grams protein) in chocolate, vanilla or strawrberry. The 16 oz. sells for $1.75 in the deli, so I'm sure you can buy them in bulk at the supermarket for much less. Granted, it's not the best quality protein or carbs, but it is very convenient when rushing to work after the gym.