Have you tried GM? Place a wanted ad in the free classifieds on this site. Hemming's? Ebay? Swap meets? Does a breather from another year Olds fit or possibly any other GM product?
Try the Oldsmobile Club:
The 2006 meet will be held in July in Post Falls, ID, near the Washington and Idaho state line, a short distance from Spokane, WA.
Good luck finding that breather.