There's not much that will stop a determined thief. There is a lot that can be done to stop an opportunistic thief. I would not settle for a single DETERRENT (and that is all they are). Cables and chains are easily cut. Most locks have a weak spot. My genny is bolted under my bus. Yes, I do run it in Sam's Club parking lots. I am a member. I ask if I can park overnight ("OK"). I ask if I can run my generator ("OK"). I ask if my choice of where I'm parked is okay or if I need to move. I ask if it's okay if I sit outside in my folding chair for a few hours ("OK"). I invariably get told to pick up some meat from the meat dept and plop it on my grill. I have been told I can stay for several days. One store wanted us to stay for over a week so we could attend their town's centennial celebration. Regretfully, we had to decline. It sounded like a lot of fun.
My second choice of overnight stays (ONS) is Cracker Barrel. I ask while we are having supper. We have breakfast there the next morning. I have yet to be told no. I have been told that I can park in the shopping center parking lot adjacent to CB and haven't been hassled.
My third choice of ONS is a freebie/cheapie public/private park or Walmart. I have only been told once not to run my generator past typical quiet hours. That was only because a neighbourhood was plastered 10 ft from the Walmart parking lot and they liked to complain about the noise. Oddly enough, they didn't complain about the screaming fit a couple of homeless people were having about all the RVs in the parking lot (It was "their" home and we were supposed to leave). Since I got no response from the store security, I called 911. Cops showed up and run them off. I have ONS in a Walmart twice since then.
Also, when there are other stores sharing the parking lot, WM does not have an exclusive right to the lot. One lot we stayed in, we parked in front of DollarTree, after asking permission. I loved the sign we parked next to. I had to take a pic.
Cops obviously used the parking lot as a shortcut. I have been told by several store managers in several states over many years that the "No Overnight Parking" signs does not actually mean no overnight parking. It for people who abandon their vehicles or put for sale signs in the windows and leave the vehicles sitting there for weeks and months.
That said, if it's so hot at night that I need to run the air conditioner, I prefer to plug into a freebie/cheapie park because I know how much fuel my propane generator uses to run my air conditioner overnight. This dictates the price I am willing pay for the use of electric. While in a park with hookups I take advantage and fill/dump as needed.
Please note, I am NOT an Escapee. I do NOT follow their rules or 'guidelines" but I will warn you that, based on a generator thread dating from when the original owner's kids took over the site, "tapping" (putting a hole in the "offending" generator) was not only encouraged but celebrated. This is when I left that forum. I figure if you feel free to damage my property deliberately, then I can deliberately harm you with the baseball bat I keep in my campers. But the posters and moderators didn't like the one and only warning I gave. Even now, I stay clear of anyone with an Escapees sticker on their RV. As far as that goes, I actively avoid other people in campers and motorhomes.