High Amp DC-DC Buck converter
You could potentially put in parallel several Buck circuits to create the current you need, but I don't suggest it unless the controller has a Sync pin to synchronize current draw. 

To be honest, it might actually be cheaper to build a custom synchronous buck circuit driven by a tiny micro controller. At 30A a synchronous buck design is a must, multi-phase might also be a good idea, though that makes it much more difficult to design. I know that's not the answer you wanted to hear, but your power requirements are too specific for a company to have invested in an ASIC for that.