Buy a copy of Deus Ex from Walmart. Take out the Onlive code and use it for yourself. Sell the rest of the package back to Gamestop as a used game. It's exactly like the "new" ones that they are selling, so they should take it.
Onlive doesn't charge a monthly subscription. They do offer a monthly rental fee for access to about 80 of the games, but that is something different. If you buy a game you get to play it with no extra monthly fees.