I need a cheap universal joint for a project I am working on so I have been playing with a few options. This is the one that seems the best so far. It is using a plastic ball from a wall track toy which is pretty far from a perfect sphere but it seems to work very well anyway. For the project I will use a cheap 1/2" steel bearing and laser cut the pieces from Delrin which has low friction. I will probably use nylock nuts on the screws to be able to adjust how stiff the movement is.
Video of it here http://www.youtube.com/watch?v=uxKQXoyVtPg
The bearing in these drawings is .722 in (18.34mm) so you will need to scale the holes to suit whatever size bearing you use.