Anyone?

There really isn't much you can do with those bars. If you found a riser that fitted you would then have your arms sloping down to the extensions.
Generally the best plan is complete replacement - basic alloy basebar and a nice adjustable clip on (like Profile Design Sonic/Ergo series).
More expensive than if you were able to get adaptor parts (if it were possible) but you get better armrests and much more adjustability