This site may have been posted before but for newer members here it is again.
I have no affiliation what so ever with this site except as a customer.
http://www.moreleds.com/railroad.htm
This is a great source for just about any type of LED that you can think of for model RR purposes.
I like their SL32F-RG LED for displaying turnout status along the track. They cost just $0.50 each. There is a $5.00 minimum shipping charge.