I use a 1 gallon jug and it works great, vortex and all. I agree, vortex isn't required by any means, but if it bothers you, try that assuming your surface is large enough to hold a 1 gallon jug.
If you have a LHBS, they sell them for $5 each I think, much cheaper than a flask. If you don't have easy access to a LHBS or don't want to spend the money, just go to your local Walmart/grocery/etc store and look for an adequate sized glass and maybe you can get it for cheaper? Otherwise, a used Vodka or Rum bottle?
Hope this helps.