Export it to nif, and extract one of Jimmy's clothes (Like P_Sleeves or something) and replace the NiTriShape data in the P_Sleeves with the one from the nif version of Johnny's jacket. Then texture mod the NFT for P_Sleeves to be the texture image for the jacket too.
You can export it to nif then just send that to me if you want, I may do it for you if you want... kind of bored atm