Im no mom, but I am an aunt and I care just as much as you all do--
couldnt you just put some clorox disinfectant wipes in your diaper bag? get a cart while youre in the parking lot, so you can keep the kiddo in the car while you give it a wipe-off.
Cause who wants their kid sucking on clorox residue?? LOL That would work great for an older kid who touches everything, and then sticks his fingers up his nose, and in his mouth, etc, but for a baby who gnaws on everything with his mouth, it isn't really the right thing, unless you could rinse it after disinfecting.
I made a very simple thing for my kid when he was little, but it wasn't nearly as elaborate as the one you guys are talking about...I just took fabric, cut it the width of the cart handle, made it big enough to wrap and velcro around the handle, and drape down to the legs of the kid, and then backed it. On the front, I sewed a strip of fabric tacked at one end, threaded LARGE wooden shapes on, tacked the other end down; tacked another strip down at one end, and made a self closing vecro loop at the other end, for attaching plastic keys, paci, whatever, and I had a couple more entertainment ideas on there, too, but it was so long ago, I can't remember that much! But it did the trick, and kept his favorite part to suck on inaccessible, as well as amusing him during the trip