the oil filter part number on my kawasaki FR691V is 49065-7007, which i found available at home depot.
and according to the kawasaki manual, sae30, 10w-30, or 10w40 is the recommended oil. my dealer said that 20w-50 is recommended now. i emailed hustler and they said that the thicker oil will be more resistant to oil consumption. plus in hot weather i feel it provides better protection.