Locking your hitch

I got mine at Walmart. I don't remember the brand but it has a hitch like ball that fits into the receiver. It was about $20.00
You could try amazon as well

No hitch lock is 100% reliable. What you are trying to do is to make yours less attractive than those without locks. The one I use came as part of a Master Lock kit with locks for the hitch pin and coupler pin. It had a zipper case for storage when these are not being used. There is sufficient room for me to carry a small container of Reese hitch grease as well. One of the best things about this kit is that all the locks are keyed alike.

I put a padlock on the locking lever for the hitch coupler.  I suppose someone could sneak a smaller ball into the locked coupler, but that'd be pretty exciting watching them try to keep it connected as they race away.  They could also cut the hardened hasp on the lock, but it's a lot of work.  I guess you could fill the coupler hole with any old 2 1/4 ball that you happen to have laying around and lock it in with the locking lever and the padlock.  Then the hole in the coupler would be filled but a determined their could still cut off the lock.  

I also keep my safety chains wrapped around the crank, secured with a padlock.  The battery boxes and propane tank are also secured with a separate chain.  It's all a matter of deterrence.  The more impediments you put in the thief's way, the more likely the thief will for an easier target.  It would only take a few seconds to cut the chains with bolt cutters, but they are costly and a hassle to carry around so you improve your odds of being left alone.

At the house, I keep the Pod on power. The stabilizers are down, the hitch is locked,   I have a nice sign on building that says, "Trespassers Will be Violated" and another sign that says I am a concealed handgun permit holder. I am a light sleeper and a veteran. I do not welcome a confrontation, but I am not shy about the consequences. My ADT signs are posted and my alarm and cameras always work. It is a shame but where we have gone. I have numerous other things on property that are secured. My advice is don't make yourself an easy target. Secure your stuff, lock your doors, have a legal defense strategy.