You say you're not a publisher, Are you a developer? (if you are simply submit it. instructions how you do that should be available after clickign the green button on the top of the page in the greenlight banner that says "submit your item")

If you are not then find the dev/publisher related to the game you wish to appear on Greenlight/steam and ask them politely to submit it.

There is no other way to do it.

Not here. You should start by contacting Eidos Interactive. In the mean time Omerta isn't a terrible substitute, if you can find it at a good discount.

ok thx, i`ll try