I have one of the AllPro http://www.allprooffroad.com/index.php?option=content&task=view&id=31 slip shaft kits. It works fine.
Since the time I bought it, Marlin http://www.marlincrawler.com/shaft.html has also put a kit in his line up.
If you have the tools needed (welder, grinder and a really big pipe cutter) it's not at all hard to do it yourself.
Mark