It took some time, but after all I can present you with:

Round Water Bucket

You are tired of always having to place the rather huge through in your selfmade stalls, so the horses have something to drink?

Here's the solution: a completely functional round water bucket. The horses can drink from it, just as with the through, and the water level falls as they do so.
It comes in three preset colors, and has two recolorable channels: the bucket itself, and the rim.
You can find it in Decor/Miscellaneous.
(Sometimes the horses don't drink right from the bucket, but to the left of it. This is due to the footprint, which is still the original. Sorry, I can't fix that right now. But you can just go to buy mode and put the horse in the right place, and it'll continue drinking in the right spot.)

Download as Sims3pack or as package.