I think that a hole of this size would be very easy to patch, you have all the access to the hole you need
I would start by putting a patch on the inside
1) cut the hole to be a bit more straight
2) put glue on the inside of the tube
3) put glue on the patch
4) work the patch inside the tube and start by applying presure to one end
5) when the patch is nearly fixed all the way round, put a little presure in the tube, to make the patch stick to the tube.
6) lett it dry off for about 12 hours, keep the presure in the tube
7) put a new patch on the outside.
You could consider putting a patch just like it on the other side off the boat to make it look like it's supose to be there, depending on where the hoel is.
Otherwise I agree with MeMe, see if you insurance company will pay for a new tube/boat.
Getting a patch this size shouldn't be a problem, just contact any of the tubemakers around.