id say most of his adidas bats were made by hawk, if you ever visit hawk, the photos of his and pietersens bats are all over the workshop. they also have a signed ian bell test shirt displayed in the shop, 'to michael and robert, cheers for the bats, belly'.
early december when i went, they had just sorted pietersens bats for this tour (unfortunately i didnt go early enough to see the bats although they were delayed in being sent to kp as adidas had none of the KP stickers left that have to be stuck under the adidas stickers), they never mentioned they had made bells but knew he was on his way to kook. They had also made james taylors bats so i can only presume they have/ had a contract with adidas.
As both Michael and Robert are quite open about talking about the bats, it kinda makes me think they're legit and is some sort of contract there. They will also be at the cricket roadshow at edgbaston in feb so if anyone goes there, ask them.