Marc thanks for the info on Two Bucks Liquor. They carry food grade CO2 and tubing. Their tubing has about 1/4" wall and they said it shouldn't leak CO2 and that it's food grade. Mike have you heard of that?
If you use the Aquarium Plants regulator you will have to slide on a piece of semi-rigid tube on the output nipple, cut it off just past the nipple and then slide the other tube over this new 'spacer' because the nipple on the regulator is so small almost any tube you use, other than the green type that's the size of air line, will fall off.