The standard plastic covers run about $10 and will do the job for a smaller bike (REI, Sporting goods, etc.). They tend to trap moisture and can be punctured. For a larger footprint, you might need to go with a scooter/small motorcycle cover. Don't trust fit charts for sizing. You might want to go to a motorcycle dealer and do a fit check. Most Motorcycle covers offer a grommet for running a lock through at the bottom.