Don't you have some growing wild in your neighborhood?  What I call sweet grass is what dogs like to chew on.  If you let it grow it gets fairly tall.

I'm from the same area as you.  I've seen it advertised on the web for $7 a plug, but from the pictures I see, I think it's the same thing as we have around here growing wild.  If you can't find any around your house, go over to the Milk River (where it crosses Jefferson by the Ford mansion) and look around there.  I'd offer you the run of my back yard to look at what the dogs chew on when they visit, but I won't post my address in public.