I've found that a push block that both pushes and holds down the workpiece on the jointer isn't easy to find. So I decided to make my own.
As you can see, the handle lets you apply downward pressure over the jointer tables. At the back, a cleat catches the end of the workpiece and pushes it across the knives.
This drawing shows how the push block is built from just three parts: a handle, a base, and a cleat. The base is attached to the handle with screws countersunk in the base. The cleat is simply glued on.
You can shape the handle using the pattern shown here. I cut the outside out first. And then I cut the out the hand grip at the back and the handle in the center. To get smooth curves, you can drill out the corners of the waste with a Forstner bit.