thanks for the kind words atankersdad. I don't have any, nor have I had to purchase any. But I do know that some gaskets and parts are still available through Onan/Cummins.
There are NOT MANY parts that you can still get though....if you could find an Onan dealer in your area maybe they could track them down for you.
And if that doesn't pan out, they should be a "flat" gasket from the looks of it (flat meaning they don't have bearing humps to go over or anything like that...a flat smooth sealing surface), but I'm not positive....Carl_in_NH would have a better read on that than me from the sound of it. But I would think if you had to replace them, it shouldn't be too hard to find some material and make your own...maybe with a good thick piece of cork gasket material
If you do find them from an Onan dealer please make sure to post where you found them, and how much they cost and new part numbers if they are different then the TM. Others could use the information.