Finally Bit The Moon Bullet...

...and bought the Mooneyes Sportster derby cover to go with the a/c and timing cover I've already had for a few years. I was NOT happy when I got the part home, however. The back side of the cast was very uneven, and had to be belt sanded level to fit evenly around the circumference of the primary. For what they charge, it should not have required a secondary operation to install.