Turn Signal Bulb - Silver/Amber

[eystein]

I would like to hide the turn signals in the cowl lamps. To really achieve this properly I will need the new bulbs that are amber when lit but only shows an external silver coating when unlit. -Just like the one shown in the attached photo.

Now - of course all I can find are 12V bulbs, not 6V. Does anyone know where I could get this type of bulb for 6V ? Alternatively, can anyone recommend a 6V to 12V converter that I could use for this application. Converting the car to 12V is NOT an option