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Any truck and fleet supplier can help you. They're used all the time for equipment. Most any off-road lamp kit uses a similar product and weather-proof product.
I've scoured the internet with searches but haven't found one yet. I prefer to attach my own wires and not use a pigtailed socket.
Then just do a JunkYard visit and grab any late 80's or 90's under-hood relays and do what you would like. There's hundreds of them just a JunkYard away. Get what you want from the latest model that you can and make sure there's a part number on it and it will ease the search for a replacement if you like what it did. You can repin the socket as you like.