I have a short sissy bar.  Much like the one in the photo except mine is a half circle instead of flat like this one. I took the original sissy bar to a welding shop and they cut the top off and just welded the same gauge tubing to what was left of my sissy bar. then they machine sanded it smooth and charged me $20  Most shops can make any size sissy bar you want for not much more than that. I had my choice of square tubing,round or twisted like a pretzel. I believe it's 5/8 inch stock

I really have to learn how to post pics. Savage Greg took a pic of my bike and you can see the sissy bar in the Motorcycle Handyman section in tailights-8