Okay this is going to sound silly but since locking up in this manner sounds very important to you, why don't you take sheets of tin foil with you wherever you go and wrap it around the section of your chainring you plan to lock against. When you are done, dispose of the foil.

It's a lot of trouble and probably not worth it. But then again, locking up that thoroughly is probably overkill too. At least it solves your problem.