What do you mean by 'kit'? Does he want to make a bow from scratch or just do the finishing work on an already made bow? Does he want a glass bow or a backed selfbow?
I know of a couple of outfits that sell bamboo or hickory backed bows that are already formed and tillered, ready for final sanding and finishing. Dan Quillian is selling them on Ebay.
Buildabow has floor tillered selfbows and backed bows, and a kit for making a backed bow.
Rudderbows has a similar deal.
There was someone selling unfinished glass laminated longbows the same way, but I don't remember who it was now.
If he wants to make a bow from scratch,
Bingham Projects is probably where he'll wind up. Another source for bowmaking wood is the
Woodshed.