Oh they make 'm alright;

http://www.alibaba.com/showroom/torsion-bar.html


But just not (yet) with Mopar bar hex-ends it seems. Most are just splined ends.
Maybe if possible, if one could make an adapter with splined internals and hex-outside, you could use the bars from a different car-brand or application.
But I would think the adapter will be too thin and might break or split, unless the larger C-body torsion bar mounts are used perhaps.