Consumer device manufacturers, including aquarium lights, almost never manufacture their own DC power supplies. You don't have to order one from the light company/distributor. You could get one that matches the same specifications.
That said- Read the DC voltage and amperage rating that must be displayed on the outside of the power ‘brick’. The center pin is almost always positive and the outside (barrel) is almost always negative. If in doubt check it using a multimeter, or get someone skilled in their use to check it for you. If you are ordering a replacement DC supply, such as from Amazon or similar source, match the DC voltage exactly. and amperage at or above what your existing one says. The connector must match the physical dimensions exactly as well.
Disclaimer: this is not intended to be technical advice. I do not have knowledge of your exact circumstance or situation. So you might want to consult a professional.
