The bars in the picture look like they could be reproduced by sliding larger i.d. extensions on to some fairly common cruiser bars, then welding and chroming (you might need to do a little bending inward to keep them more parallel). To fit standard throttle and clutch controls though, butt welding similar o.d. extensions would be better.
BTW, I know this post is a year late, but I'm in the market for the same type of bars and I was hoping I wouldn't have to go through that much trouble. Did you ever find what you were looking for?