I am not aware of any dealership/factory option that would include the ball. There are 3 common size hitch balls - 1-7/8", 2" and 2-5/16". Doubtful you would be pulling a trailer with a 2-5/16" ball that is under 5000 lbs. Most hitches under 5000 lbs are now 2", 1-7/8" is becoming less common. It is because of this that the ball is not included, because not all trailers are the same. I have 2 different hitches, that have dual adjustable height balls. Once has a 1-7/8" ball (my Dad still has a couple of trailers with this) and a 2" ball. My other hitch has a 2" and 2-5/16" for my heavier trailers. I only buy Anderson Rapid Hitches now. They are aluminum so they don't rust, can tow up to 10,000 lbs with 1500 lb tongue weight and they can be be used as a drop or raise hitch to accommodate different vehicles and trailer combinations. Link below
View the best Rapid Hitch here. Shop with us today for high quality trailer hitches and gear that is strong and versatile.
andersenhitches.com
You can source just a ball for the hitch that was included. Measure the opening diameter, most hitches balls have a 3/4" or 1" threaded shaft. Purchase the ball size that fits your trailer and the threaded shaft that fits the opening of the hitch. Also keep in mind that your trailer should ideally be level when towed. The hitch you received with your tow package may not level your trailer correctly.
Side Note: It is really tough to type all of this stuff about balls and shafts and not giggle inside a little.