Hi, sorry to hear about the flapping bago, I know not funny but hey if we don't laugh we have to cry so might as well get a laugh in.
As to how to get a piece, if you can perhaps gingerly pull out a piece from under you can recreate it. If I recall correctly it actually a two or so piece sandwich, that could have had some adhesive put on during manufacturing, but I am not a corporate employee just an end user.
Any way if you can ferret or fish out a piece/pieces out from under there, you could recreat them from foam blocks for sure. Thanksgiving is just around the corner and you can get some carving practice in with the electric turkey knife. Yes that thing cuts foam you have to let it do the work not force it. Similarly if you need cushions it does that well too!
If a lot of pieces (large section) is/are gone you may build a jig with a hot wire.
Eterna bond, and please paint a no step/walk zone notice on your roof to remind you and others when you are not there.
BTW a manufacturing corporation employee on this forum states that after 7 yrs of so the manufacturer basically washes their hand of the pile of parts they put together, as it is they do not provide a unified one point of contact for the warranties which thank god our car companies are providing so far (except for tires and battery) that is, though Hyundai even stepped to replace tires for customers when the design was bad. They also warranty their cars bumper to bumper for 5 years and 10 yrs 100K for drive train as does Kia. More manufacturers should be made to do this and if the RV industry gets any where near there it will be ohsogood.