There are some on line companies that sell "pet Safe " antifreeze at insane prices. It is no different from the Peak product Sierra that you can buy at automotive stores. They are all propylene glycol. The automotive grade or marine engine grade have the same inhibitors as regular antifreeze. Camper antifreeze doesn't.
Propylene glycol is still somewhat toxic in high doses, but is way safer than ethylene.
Side note, about 17 states have passed laws requiring conventional antifreeze to have a "bittering agent" added to make it taste bad, however since it only takes a tablespoon full to kill a medium sized dog, it's still too much of a risk. I don't know if that applies to the safer types but that would be even better.
