I don't have anything yet with a stick shift but I've been checking out what others have done and seen some interesting ideas. I fly a lot of kites and I use several different kite stakes. One of my favorite kite stores has these neat billiard ball stakes and I've got a couple of them and thought they would make a cool shifter handle. These are not full size billiard balls but 1 1/2" diameter.
http://www.intothewind.com/shop/whats_New/Billiard_Ball_Kite_Stake
http://www.intothewind.com/shop/whats_New/Billiard_Ball_Kite_Stake