It should be an easy repair you can swing the sewing machine inside the leading edge via the zipper, or hand sew it. . I can't imagine it would cost more than $20 for any tailor (or sail repair shop) to do.
You will probably have to supply your own velcro.
Nothing wrong with wanting to keep your kite minty.
You could also send it to a kite repair specialists but then you are talking about a big shipping fee.
Or take it to any local guys that can do kite repairs.
Remember when you go to your local tailor or sail maker, they will not know anything about bladders you might have to take it out for them before you give it to them, or make sure they don't accidentally puncture it.
If this were my kite I would buy some velcro and sew it on by hand myself. If you don't own any polyester thread you can use dental floss in a pinch. Cotton thread doesn't weather as well as a polyester thread. Such a small repair I don't think I would bother setting up my sewing machine.