How does the top cover bolt down? One Screw or two wingnuts? The Briggs part # you gave doesn't work for me. Below is a pdf from the Briggs site.
Single bolt-496599 changes to 691401
Two wingnuts-398826 changes to 495617
Where are you located? I should have one or the other on a parts engine. Or, you can order for under $30 here: http://www.outdoordistributors.com/