ah this one, was just sold at ebay right? I think this one is not complicated and you dont need a specific crystal. just get the size of the current one and order a similar one through one of the many watch part pages. A Diver plexi would be recommended.
I was going to bid on that one but it finished in the middle of the night my time. Not a bad price the OP landed it for, especially if a replacement crystal isn't that hard to get!