No part number, but here is a website with some similar. I thought they were only 3 " long or so, guess they are actually 6-7", you may have to go with your round if you don't have the room.
You can use the filters on e-trailers page to see what may work. I think we had a 10 or 12 bulb LED that had a flange around perimeter and used a rubber gasket that holds them in the trailer, maybe submersible as they were completely sealed and we had to buy the complete light housing.
Mine was alot cheapr though than listed, try a local trailer shop if any around you.
Here is a similar trailer.....