Overton's lists this single plate
. They also list a 14" wide one.
I'd pick hydraulic over an electric one is you plan to keep it a long time.
The size you ask for is just about that of the Sanger model by Bennett which you could get through one of their dealers. You would also want to check out the Supra dealers to see what they have.
You will be very happy when you have switched from a fixed plate to the adjustable one. You want two actuators if you have 20" of width.