My son is 17 months and I put him in this Graco seat http://s7d2.scene7.com/is/image/GracoBaby/1812931?wid=600&hei=450&op_sharpen=1&resMode=sharp 2.
It's one of the few that fits and still gives your front passenger room. The only downsides to it are that you need to use a rolled up towel to get it level in the "green zone." I would also recommend getting one of theses to put under the seat to avoid any marks from the base on the leather.
https://lh5.googleusercontent.com/public/25YVIbzSUdf5a8GX22m09bZJd2AJS2BiDf07RW_jNBi1lOp4uU 1Bs1d8qPJ-9rWZ1sdzO_7aVBsoTWeWV2UcX26-lUuNCQ8czBtavipKDsstkbNk5nAi9HE2EUpglhKAEU92vkVIMW 21FsHZ6EMOvvC5DqE1gVUVhTtk5NOV5oh6K-oMIZfN=s150-c
2013 E92 M3
Space Grey/Fox Red Novillo