Did you check that nothing's come loose?  Sometimes the bolts on the rear sway bar or front sway bar come loose.
I'd also agree with a previous poster that not all front alignment shops are created equal.  Sounds like you've done everything possible to stop the wandering.
I think it's worth bringing to a good alignment shop with a rack or well and double check that you are not toed in or out.  Have them check all the connections on the track bars and sway bars while they are looking at it.
I guess you can try the steering stabilizer, but it did nothing for me.