The problem with any brand of feed that has "treats" and things other than pellets mixed in is just that- the chins will pick out the good tasting stuff and leave behind the pellets. It's like handing a child a plate of broccoli and chocolate- they're going to eat the chocolate and leave the stuff that's good for them. Not to mention, they usually contain many ingredients that are actually not healthy or good for chins.
Oxbow is a very good feed and can be found in many pet stores. Other brands are Mazuri, Tradition, and some rabbit pellets such as Manna Pro Sho and Nutrena Naturewise, which can be found in feed stores or bought from various members on here.
He may boycott the new healthy pellet for awhile, but healthy chins won't starve themselves. Once he realizes he's not getting the food with all the yummy treats mixed in, he'll start eating the pellets.