I have used different SKB soft cases for years with different keyboards. Fot the T4 I use the SKB 61 soft bag, mainly because it's light and therefore easier to lift out of the van and into the gig. But, because it's soft you have to be careful with it.

Also I had to cut down the foam at the end just a little to make it fit better.

http://www.sweetwater.com/store/detail/SKBKB61/