Marine Exterior Lights on Seaside Home
Yes there are stainless fixtures but for the cost I would probably just purchase currently available led floods or wall packs. The fixtures I use are aluminum but are universal voltage rated 100-277vac. 

These low wattage high lumen output fixtures are so much less than a stainless fixture you could replace them 1/2 a dozen times and wire them directly into your existing power. 

Look at what is available at myledplace.com or 1000bulbs.com both have a good selection of DLC + UL approval  of LED fixtures I have used both and have had good customer service even on the few failures I have had. dlc is design light consortium and requires a 5 year warranty and you want UL for use in the USA.

The reason I suggest a less expensive aluminum fixture is because the electronics usually don’t last as long as a stainless fixture and the non stainless parts inside usually fall apart requiring repair so all the big $ is kind of wasted where a good aluminum fixture will be much cheaper easier to wire so give them a look.