He can use spinnaker tape, or sail number tape.
Very light and very strong.
Then he can go out instantly !
The kite has to be totally dry and clean locally, before mounting the tape of course, to get the best and longest adhesion.
You can even get spinnaker tape in many different (matching if lucky) colours
Sail number tape (black or red) has better adhesion, and will be a good permanent solution.
If it is a long cut in thick front tube material, you might even use a couple of layers of tape (over a bigger area, so the adhesion is bigger or equal to the breaking strength of the tape...)
A sailmaker should be able to sew a patch of dacron cloth to your front tube too I think, but because you cant get to the inside - it is only if one has the right sewing machine of course.
And you have to take the bladder out - not necessary with the tape solution.