One pitch that you might try is the forkball. It's very difficult to master as pitches go, in fact the learning curve is steep and can be drawn out. But, this pitch for some are a career saver. On the other hand, this is NOT a split-finger pitch. I can expand on that later if you wish, but for now, focus on the feel, witness the trajectory and results, and so forth. This pitch does require a lot of strength in the hand, grip wise. Also, this pitch is not for everyone. Shoulder strength and a deliberate body language during the final delivery stage of your motion is mandatory.
Below is a graphic picture of the front and back view of the grip along with some narration.
I should mention that I really wouldn't classify this pitch as an off-speed or changeup, rather a way to take the kind of velocity away from your current situation, as such.