After a great deal of searching last year I finally found a suitable motorcycle Pet Carrier for our 11 lb LhasaPoo - Tia. She lug's it and now has logged close to 3000 miles.
The Pet Palace comes with two inside D rings to tether to her harness, a pocket for any standard collapsible bowl, two water bottle holders and two pockets for misc. food, brush, lease etc.
I'd probably pick up a wags trailer for my Shepherd if I could find a used one for a decent price. Hard to come by. As far as carbon monoxide goes, I'd hop in it for a while and have a friend tow me around to check the noise, fumes etc. If I die or lose my hearing I wont put my dog in it