Is there a way to get water into the nether?

The easiest way is to build a portal nearby, travel to the normal world, fill your glass vials with water there and bring those back to the Nether. You can fill as many vials as you can fit in your inventory and it won't take much time out of your brewing schedule.

You could also keep water in the Nether in a cauldron, but as that only holds 3 vials worth, it's slower than simply bringing the water to the Nether in vials.

In versions of Minecraft before the current 1.0.0 release, you could use the Silk Touch enchantment to get Ice blocks, and break them in the Nether to produce water source blocks. However, this was patched, and they won't create water in the Nether anymore.

The only way to place water in the Nether, currently, is to place a Cauldron and fill it with water. Sadly, it isn't as good as an infinite source, as it can only fill 3 Glass Bottles before needing to be refilled, but it's the only option for brewing in the Nether at the moment.

Create two ender chests, keep one and one world and the other in the nether fill it with buckets of water you can keep up to 27 buckets in an ender chest it's the easiest way to get water in the nether.