I think Harbor freight has some prebuilt kits like what you want in LED. They might not be magnetic mount though.. Don't start drilling holes in your ROPS or the Safety police may track you down and smack you around.
I haven’t used these guys yet but intend to soon for four LED Strobes.
Look threw their stuff, they have a lot of different sizes to fit just about anywhere on your tractor.
The last storm got me thinking about more emergency flasher lighting.