That is a real "hole"... WOW.
But you have options and need to do something as that is insulation exposed that can get wet and create great havoc with water intrusion in short order.
Can you measure the left to right and up and down size of the hole? It looks like 1 1/2" long and about 1 1/2" high. Maybe 2".
1. For a real fast something to cover the hole before a real fix is made, use a piece of Gorilla tape to seal out any water. Clean the surface well, then apply the tape. Make sure it is Gorilla brand. This will hold for a few months but is not permanent. The sticky adhesive once you lift the tape can be removed with mineral spirits.
2. By the pics, this hole is on the bottom piece of siding. Wow what luck.... as this piece is the easiest to remove verses a hole 2 feet up the camper. If wanted, you can remove the bottom piece of siding and replace it. This creates a back to new situation but is a lot of work and time and then matching the paint faded color will take some work. If this route interests you, let us know we will need to get into where to get the siding and how to remove the siding and put back on.
3. As ggrvguy above stated, get a piece of aluminium flashing and using small pop rivets, rivet the patch on. If you can fish the aluminum inside the camper verses outside it may help make this more cosmetically cleaner. This fills the hole but is not yet water tight. To create a permanent water seal;
3A. You can put a piece of Eternabond tape over the entire patch to cover it and seal to the original siding.
3B Use some auto body putty that is water rated and cover the area, sand smooth and paint over it.
I'm sure there are other ways some have used, those came to my mind first.
Hope this helps
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC
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