Keep digging. You are going to find a lot more about what you are not supposed to do, and much of it is going to be local interpretations. Much of this has to do with the caution that stumbling anyone is grounds for Gehenna. Such "stumbling" is their way of making sure you are not doing many things otherwise not mentioned in their rulebooks.
Buying Girl Scout cookies is just one of these things. Some that could be imposed locally based on one person's interpretation may include proscription of eating certain foods associated with holidays (eggnog and candy canes top this list), listening to any music except the 135 Kingdumb maladies (could stumble someone), going online (this could in fact become an official ban but many congregations still view going online as bad), buying silver or gold (too worldly and not trusting in their god), and preparing for "time and unforseen occurrence" (or, in my case, time and forseen occurrence) (not trusting in their god). Getting nice things could also be viewed as materialism. And there is no structure to these bans--you could be banned from doing something and they come up with a lame excuse why you can't but others can (such as that you are held to a higher standard).
Which they could upgrade from merely hounding you to disfellowshipping. All it takes is for them to hound you once about these items. You buy a good flashlight because yours died last time you got a blackout. So they hound you because "it is materialism and not trusting in their god". You don't get rid of it, and next week they call it "brazen conduct". That can be used to enforce any rule, even if not in the official rulebook. It is often applied capriciously, too--you could be put out for "brazen conduct" for something someone else is doing openly without issue.