These are beta switch lamps to fit a Lionel Fastrack switch that has the swtich stand removed and the hole drilled out to 1/8".
You can purchase a bi-color (RED/GREEN) pre-wired 0603 SMD LED off of eBay that measures 1.6mm x .8mm and should fit easily inside.
Good Link at the time I am posting this:
10PCS 0603 1615 Pre-soldered Bi-Color Red Green Light Pre Wired SMD LED Diodes
ATTENTION!! THIS IS A BETA .. HAS NOT BEEN PRINTED SO ORDER AT YOUR OWN RISK UNTIL WE CAN PRINT ONE AND CONFIRM.