I don't know if the specific bulbs are availale for the Box, but I did the clear mod on a 997 and got bulbs from HOEN. (
http://www.hoen-usa.com/)
They appear clear - 'till you turn them on. They have a section of yellow you can't see normally. Perhaps the best lamps they had, in my opinion, were license plate replacement bulbs; they are 'blue white' vs. the yellowish ones from Porsche.
j i m