This review on animal models of NAFLD/NASH might help you. It gives a nice overview and also the advantages and disadvantages of the models used. There are several dietary NASH models, so you can try to use those if you prefer non-GM animal models.
we developed a mouse model (B6 mice) where we put them on a high-fat diet and degassed 7Up (fructose). These animals establish prediabetic traits much sooner than just high-fat alone. One issue- no fibrosis.
It is interesting that there is a sexual dimorphism. I just found out that a low-methionine /choline deficient diet is much more milder to the mice in terms minimizing weight loss.