I've been using a 5-gallon water bottle for two batches of Skeeter pee. It happens to fit a standard 5-gallon carboy cap
. The cap is tight enough to allow the airlock to bubble, which means it won't let nasty critters in. Unfortunately the seal is microscopically loose enough to not work when I blow air into the cap to force the liquid through a racking cane -- the pressurized air escapes out the bottom of the cap.
The bottle was available at the local big box store for $7, near the water filters. It is marked as food grade.
There have been no big, flavorful beers in this bottle yet, so I can't comment on its ability to resist absorbing stuff.