Does anyone know where I can obtain radio display bulbs for my 1996 3000 GT?

The original cassette/stereo radio (Infinity amp/2 DIN) display backlight has finally given up the ghost.  Replaced the original bulbs with new 6.5 V bulbs that could fit the bulb holders, but the display is now very dim.  Apparently the original bulbs are a lower voltage.  I need to find the correct type bulbs that were identical to the originals, both in design and voltage to get the proper brightness.  I may be able to find the bulbs in a junked radio at a salvage yard, but the age of the bulbs would be a concern even if they still worked initially.  Any help with this would be greatly appreciated.