https://www.mouser.com/ProductDetail/Vicor/BCM4414VG0F4440C02?qs=sGAEpiMZZMvGsmoEFRKS8Koqt8Pjkl395UH5y7vpjkRmt5B2nKmGcg%3D%3D

Still available, now it's $1000. Adjustable voltage, 40 amps, up to 700 volts in and can handle surges well beyond that, also you can just add more in parallel if you need more amps. Fully isolated between in and out. About the length and thickness of a cell phone but half as wide. Data sheet suggest this is already in use in transportation applications.