I found this on TBN. Don't know how accurate it is but you might try following it to see if you can find the parts. I doubt that you have brake lights that are enabled. Here it is:
"Gentlemen, this will blow your mind. Kubota's L series DOES have provisions for working brake lights(at least the Grand L does). However the switch is not available on the parts lookup for US dealers.
Under the dash follow the brake pedal up to the top, there is a small bracket with a hole in it for the switch to mount in. There is also a 2 wire pigtail with a molded connector there. Jump the connector and the brake lights come on. The bulbs behind the red lenses are 2 filament bulbs (1157 type). Now as with some of Kubota's parts, it is probably the same switch used elsewhere on the tractor such as clutch safety,etc. but I haven't tried that yet."
