Ohhh. That's a tough one. I've found some nice LED bulbs, but it's been so long I don't know if I can find the reference for them.

Those should be GE1449 bulbs. Surprisingly, I found an Amazon listing for them: https://www.amazon.com/CEC-Industries-Bulbs-G-3-5-shape/dp/B00JNFBZMU

I did find some LEDs too: https://www.amazon.com/Keiurot-Address-10V-30Volt-Flashlight-Landscaping/dp/B0BB28YDRP

https://www.amazon.com/Miniature-Bonlux-Dashboard-Replacements-Flashlight/dp/B07WR892CQ might work too, but they're spec'd to 12v and might have a shorter life. These look nicer for locos though since the LEDs are on the side of the bulb.

LEDs are also mostly just on or off and there isn't much in the way of brightness in my experience.

It might be tempting to just use 12v incandescent automotive bulbs that will fit, but they will run hot in AF trains and potentially degrade or melt the plastic body.

Good luck.