Search? You have to use CreateObject to attach it to the bottom of a vehicle. I recommend using a pre-made script:
pawn Code:
new neon;
new neon2;
new car = GetPlayerVehicleID(playerid);
new Float:X, Float:Y, Float:Z;
new Float:rX, Float:rY, Float:rZ;
GetPlayerPos(playerid, X, Y, Z);
neon = CreateObject(18647, X, Y, Z, rX, rY, rZ, 3.0);
neon2 = CreateObject(18647, X, Y, Z, rX, rY, rZ, 3.0);
AttachObjectToVehicle(neon, car, 1.0, 0.0, -0.5, 0.0, 0.0, 0.0);
AttachObjectToVehicle(neon2, car, -1.0, 0.0, -0.5, 0.0, 0.0, 0.0);
theres have already the position of the neons just change the object id to the color neon you want ^^