I'm not sure what your cost tolerance is but we have been having great success at work with a product made by Steelcase called "AirTouch". This is a height adjustable table desk allowing the individual to move the surface at the touch of a button to whatever height they like from sitting to standing height.
Several of our staff have chronic back problems and the ability to stand or sit has increased their comfort greatly.
Their web store only sells the smaller desk but you can submit a request and a dealer in your area will give you a call. This way you should be able to get access to the wider variety of shapes/sizes available. They have a nice split-height corner piece as well as a split height rectangle top giving you a very stable keyboard surface. They also have a really nice boomerang shape which would bring the sides of the surface closer to you body. These desks are made to be used with monitor arms and are very sturdy.
Go to
www.steelcase.com and search on AirTouch for the full brochure and gallery.
Good luck finding something that works for you.
