For the short term, mountain bike bar ends can be installed on mountain bike bar ends. There are a variety of shapes from straight to curved. Most are the same size as handlebars so they can be 'stacked' to get you more upright. The possible positions are nearly endless. The main down side is relocating brake levers.
Riser bars are made in 1 inch, 2 inch, 3 inch, 4 inch, 6 inch heights. At some point you will need to get longer cables.
Extreme rise would be BMX bars. 10 to 16 inches of height. Note that some bmx bars have 7/8" clamp areas, others are a more normal 1".
As stated above, the Cannondale stem is not easily replaced.
Early Scott mtb bars came in some pretty unique shapes.