First I have naturalistic tanks and added one of these a month ago for when I'm away.
http://www.pet-tech.com/products/liv...category_id=31
It holds two cups and so far it works and looks really good. I have many mag-natural products and I'm have been very pleased. Even full my Juv BP can lay on top of the dripper and it is solid, no moving. They come in three choices but I suggest the corner bowl option unless you have a really tall tank. You could also get the dripper to drip on plants or branches if that is how your animal usually drinks.
Second if you are not so concerned with looks Zoo Med makes drippers called Liittle Drippers. They come in different sizes and are pretty cheap. I have not bought one yet but plan to soon. Amazon has them in all sizes at good process. I have not seen them for sale in any store.
http://www.amazon.com/Zoo-Med-Little...little+dripper
That link shows only one size. On Amazon under pet supplies search for Little Dripper and they will all pop up.
I think either of these are more suited for what your looking for. Hope this helps.