If you find the actual #, it would be nice to nail down the part # once and for all. From the Brasseuer site and from the MTH Light Bulb chart:
Would be good to know if indeed the passenger car bulb is different/larger than the Realtrax track/switch bulb.
As my Realtrax switch and lock-on bulbs fail, I unsuccessfully look again to see if someone has come up with an off-the-shelf plug-and-play LED replacement. Until then, I replace them with a DIY LED contraption...not a recommended alternative - do not try this at home.