On Dec 5, 2011, at 4:26 PM, Jonce Fancher wrote:

> He made up the Incredible aluminum covers with a
> finger tab and rolled lower lip.

Been tracking this thread and thought I'd add an option since
Jonce mentioned the aluminum fabricated one. I've attached
a link to my Flickr site that has a pic that is probably barely
good enough to get an idea of how this one sits.

Made by an AA airline machinist in Dallas, given to me by
Mike Boland who worked with the fabricator.

http://www.flickr.com/photos/syncronaut/6462855697/in/photostream/lightbox/

Since I don't use the vent, that cap stays on as-is, held on with the wing nut.
It's screwed on tightly so has never been kiped. ;-) As has already been
described in this thread, the SS vent plate was removed, center-drilled
and a small bolt put through it. No leaks.

Bob