I finally purchased a Shindo Yoshin Ryu bokken from Tozando online. As you can see in the picture below it just so happens it is the same length as my custom made sword (which is quite long due to my height).
TSYR uses a sword with a longer tsuka (handle) and a deeper sori (curve), which in turn means the bokken must mimic this. In fact the dimensions of the blade determine how some of the kenjutsu techniques work.
Up until now I have been using a VERY old aikido bokken that was too short and had been taped in three places to prevent the blade splitting. Sensei has been kind enough to let me use a TSYR bokken that belongs to the dojo from time to time to allow me to improve my technique.
I'm looking forward to using the new bokken in 2014.