What I was asking was did you try MTB riser bars. Most MTB bars, actually all of them, will accomodate grip shifters.
Do the VO and Nitto bar use a 22.2 or 23.8 dia bar? I've got some nice old 4 finger MTB brake levers waiting for a place to go.
Both are 7/8".
The Jitensha bar requires a road-size stem.