If you have not fixed the spreader lights yet, here is where I purchased the switch:
You can find the switch at CooLight.com the following part fit my 2004 30' marlin spreader/courtesy light switches perfectly.
Items Ordered: Price: Status:
• 1 of : Judco 188-1 Pushbutton Switch on/off $3.90 Shipped
I think it was through Amazon, but now sure of that. Just save the rubber covers as they new switch does not have the cover. The order was shipped quickly.
It was difficult to get at the through bolted mounts. The lens was difficult too. If I can figure how to load a picture I will. I took one so that the next time around I would know how to get it apart. I replaced the courtesy bulbs with LEDs one white and one red as you can see from the picture. Good luck.