Never fear!
I do have the big O-ring gasket too. I can see how the cork one would work though.
Stan! The bolts, I did order a new set from Phil. They appear to be a standard size 1/2" bolt you'd be able to get at any Hardware Store. What's different on these though is what appears to be the washer. They seem to be attached to the bolt. I got "the set of 6", 2 long and 4 short, that fasten the tub but that doesn't include the 2 used in the center of the plate. So for those I may look at ACE and see if they have any that look like these. Or, pick out the best 2 washers from the gulmite set and re-use then. Better yet, re-use them on part of the tub not connected to the power unit and use 2 of my new one for those. That way if I have a faulty seal it's just a leak. Where as if one of the washers over the Power Unit leak I get water in the transmission.
Been there!, Done that!