I do not, but I bet the shop would be able to give you an idea of the ounces in each cup. Or, have you tried googling the place you go to, for nutrition info? You could probably find some basics that way.
I'm having a little (OK, a lot of) trouble eyeballing portion size when it comes to self-serve frozen yogurt, probably because a) it's self-serve and b) it's so free form... Anyway, as a kind of visual reference point, I was wondering if anyone has an idea of the size of those little sample cups they have at the shops for you to taste the different flavors? That is, any clue how many ounces of yogurt one of those little samples holds?