I recently got one of the newer-style Neu motors (1512 2.5d) with the screwed-on endcap. Since Mike's Neu covers (which he doesn't seem to stock anymore) won't fit, this is what I did:
Front:
The motor mount covers the majority of the large motor holes, but there are some openings which are still exposed. So, I took a really thin sheet of aluminum and drilled the necessary holes. It will be sandwiched between the motor and mount so it doesn't need to be strong.
Rear:
This one was a little more involved. I tried using screening, but wasn't happy with the result. So, I tried a rigid version and didn't like that either. So, I cut up the failed version, added a dab of shoe-goo (just to help hold it in place while working on it), and then used heatshink to secure it there. A little trimming of the shrink makes a nice clean look. The end-cap screws help hold the shrink in place.
If anyone still has one of Mike's original Neu covers, you could just cut the "lip" off and do the same thing - and it would be better.
Here's a pic of both parts:
Hope it gives others some ideas...