Bummer, you're still looking?
I tried google, to no avail. You might try contacting Olympus directly. Or try one of the dealers (Helix, Reef Photo, Adorama, B and H Photo) and ask if they have the item in stock. If not, then ask if there is a similar sized camera housing, with o rings available, and try to substitute. Many of these housings are pretty close in size and shape. There were many instances where only a few buttons changed position. However, pretty close might not be good enough, so test the housing empty before you try it with a camera.
Another alternative is to contact Olympus for the o ring specs. Then look for an O ring manufacturer. You might be able to get something made for a reasonable price. It wouldn't necessarily have to be made of silicone rubber either. Butyl or neoprene should work just as well. If you have to buy a minimum quantity, the extra stock could probably be sold on this board.