You will get a good amount of milk from a Toggenburg or a British Toggenburg, if you look at them ask the breeder/seller if they are registered, that way you can check their pedigree and have an idea if they were bred for milk yield.
But it depends how much milk you need, I get a total of between 4.5 and 5 ltrs a day in total from a BT type goat and a Golden Guernsey. And it is quite a lot to use up... especially as everything else is still very busy on the holding, the freezer is being cleared in preparation for the pigs in Sept, and there is only so much soft cheese we can eat... but great fun and I love my goats!