But OP already mentioned the X Station in his first post.
good point. I recorrect my standing corrected.
Does an old SH-101 have any midi? hard to control VSTs without it I would think. My Oxygen49 doesn't need any batteries since it is powered via USB, features 8 sliders, 8 knobs, and one volume slider. I guess that is considered portable - but doesnt inlcude sounds IN IT.