Ken,
Out of curiosity, in what application would you want to use them?
I believe the tabs you're referring to are manufactured for/by Lionel. I haven't find them on their parts site. Maybe you could call their customer service and inquire.
If you simply want to be able to easily disconnect wires from the track and you're ok with soldering, the 110 Faston connectors are also available in male , which could be soldered to tabs underneath the track.
Failing all that, the least expensive way I know to acquire the tabs you're asking about is to extract them from 6-12073 1-3/8" Straight track or similar...