You might be able to find a coil through a homebrew supplier. Someone who homebrews might have use for a "wort chiller," although I have never needed one. For an example, see: http://www.homebrewit.com/aisle/p/5006. Your tubing to the chiller would need to be sufficient to withstand the heat, but the chiller should work well.

If you want something that is portable to use a still, why not a solar still like: http://www.landfallnavigation.com/memss.html.