The high mount brake light is a sealed unit of LEDS similar to the rear tail lamps - you cannot replace just one LED bulb.
A few of us were looking into installing a gizmo that would make the high-mount brake light flash 2 x and then remain on when braking. The gizmo is cheap enough, but we found out that to get to the high mount stop light you have to remove the rear seat, the trim around the rear shelf, and then remove the shelf and flip it over.
Here is the FSM that confirms this.
http://www.nicoclub.com/FSM/M/2007_M45-M35/
Open Ei.pdf and go to page 42.
1. Remove rear seatback and rear seat cushion. Refer to SE-177, "Removal and Installation" .
2. Remove rear seat belt floor anchor bolt and rear seat belt shoulder anchor bolt. Refer to SB-31
3. Disengage child anchor cover front pawls, and then pull out child anchor cover
4. Remove rear kicking plate inner, rear wheelhouse garnish, rear pillar finisher. Refer to EI-37
5. Disconnect high-mounted stop lamp harness connector from front side of rear parcel shelf finisher. (Models with rear window sunshade)
6. Remove rear parcel shelf finisher mounting clip using a clip clamp remover.
7. Remove the following parts after removing rear parcel shelf finisher.
INSTALLATION
Install in the reverse order of removal.
That was wayyyyyy too much work and drama for me just to make the light flash before staying on. Of course, your situation is different.