I made myself a wakizashi-size bokken, to go along with my regular katana-size bokken. It will be of extremely limited usefulness, but never mind, it was something to do.
The scrap of oak I used was less than optimal, with very coarse open twisty grain. I doubt that it would survive very much bashing, but I don't foresee it ever being likely to have to. I think that if it came to it, I would be best off to just remake it, using a decent piece of wood.
It is 540mm long, and has been ebonized with iron acetate.