I think any company that supplies standard rodent diet can also compound and supply the high-fat diet; but you may need to give them specifications (of the relative composition) as it applies to your study.
I saw an article where the high fat diet they used was sourced from Research Diets, New Brunswick, NJ (D12451 (45% kcal as fat, 4.7 kcal/g); I hope this helps.
We get our high fat diet from TestDiet. In attachment you can get the specifications, and they also offer different formulations, depending on the % of energy coming from fat sources.