If you have an account with commission junction then there you can find atleast 3 or 4 europe car hire affiliate programs to join. One of them is EuropeCar.com that I think only offers affiliate program through CJ.com Try them. They have a decent payout.
Hello, You can give a try to our programme http://forums.digitalpoint.com/showthread.php?t=1806170 too. Because we've recently launched it and looking for good affiliates to partner with.