I think you are officially too late. You get Paine's Full Throttle from Tromell in Macalania Woods. But in Ch 4 you don't have access to it, and in Ch 5 he will be in Guadosalam (if you get an Episode Complete in Mt. Gagazet, if not he still shouldn't be in Macalania). Also, you will get the Unerring GG from him as well. Two birds, no stone.