If I'm not mistaken, the way Sony have their cases set up, the PSU is in a cradle type thing that clips into the case neatly so you may need a Sony one. Firstly check to see if the PSU can be removed from the cradle, and if it can, a standard one may fit. However due to the space saving cases most Vaios I have seen have, you may need to get one from Sony spare parts or such like.
Let us know how you get on in case any one else blows a supply!
