Replaced our aisle and step bulbs about two years ago with LED from: https://www.superbrightleds.com/cat/...acement-bulbs/
I believe the style was called "Festoon Base" - just match up the size to find the correct bulb. F30-WHP-12V bulb fit ours - they are 30mm.
The design of the fixture makes it just a little tricky seating the bulbs but LED works great and should last many years. Ended up replacing the rest of our house/basement bulbs with LED from the Cabin Bright booth at the FROG rally this year.
Hope this helps