I’ve helped a mate with an almost identical repair, few years ago now.
£40 quid repair kit from eBay, a long evening with sandpaper and dust masks, couple of hours chopping bits of carbon fibre sheet up and sticking it down with epoxy, wrapping it with tape and leaving to dry. Then sand it back smooth (ish) and 5 or 6 coats of rattle can paint.
Think the hardest thing was getting something into the tube, behind the repair to make sure that we had something to support the bottom layer of CF. He’s moved away now, but think he still has the same bike.