This was my Friday the 13th project, and it almost turned out that way. I found these 4 1/2" LED bulbs on eBay:
http://www.ebay.com/itm/Pair-of-LED-Sealed-Beam-Replacements-4411-John-Deere-AF3892R-Tractors-Combines-/321561165778?pt=LH_DefaultDomain_0&hash=item4ade89ffd2They are advertised (at a higher cost) for Harleys and metrics with 4 1/2" running lights by another eBay vendor.
http://www.ebay.com/itm/Harley-ROAD-KING-ONE-PAIR-2-OF-LED-PASSING-LAMPS-RUNNING-LIGHTS-/141373110984?pt=Motorcycles_Parts_Accessories&hash=item20ea7e7ac8&vxp=mtrSo I pulled the trigger. Received them yesterday and was excited to get them installed. But then the Friday the 13th thing kicked in. They are just a smidge too deep to fit in the Cobra housing. Well, crap. I was hating it, they were bright and pure white 6000k like my LED headlight. So I decided to take the bull by the horns. See the round aluminum protrusion in the second pic? I pulled the 3 screws so I could look behind the heat sink. As I'd hoped, the round protrusion was hollow aluminum. Pulled out my multi tool and cut it even with the cooling fins, and put a glob of silicone in to keep the elements out. Perfect fit! Perfect color match with the xenon white headlight. About 3000 lumens each, and only 18w apiece! Now, on to the blinkers (I know, new flasher required).