Cass-
I Used a Tyros softcase that I bought with the Tyros 1 & 2 for the psr3k when I had it. I had some of the foam insulation/molding material left and just added it to either side and I think it fit fine.
I've used a heavy wooden case, back when I used a yamaha P-200 digital piano and it was CRAZY heavy...
The P-200 weighed 66 lbs, and the case weighed in around 38-40lbs.
I don't miss those days!

------------------
Bill in Dayton