I had great difficulty finding these as most Teac Tascam rails run just above 6 volts and even higher when a few bulbs have blown so for myself I managed to source an 8 volt Axial lamp with a body about 20mm long.

You need to not cut the ends before soldering and I advise you to leave on if room there, when soldering them use a thin nose pair of pliers between the lamp and where you are soldering them, as that will shunt some of the heat away from the bulb

Nice old skool glow

bulk pricing available a couple in a jiffy is ok but more they really need go in a box to be safe