After getting a shiny new cover, I didn't want it ending up yellow and crazed. Looking around, I found some 1/8" tempered Masonite and some old house primer.
Well, it won't let me upload any pics, but this is a chunk of masonite the width and (almost) full length of the pump with a 3" slot for the pressure line.
Slip it on from the front (so the pipe slides through the slot) and you have a cover which does not block the vents on the motor.
The paint seals it against weather (In case CA ever again sees rain).
If you have high winds, a small bag of shot will hold it reasonably well.
Here's a couple of shots: