My experience with ruby devs is that they are usually employed and not actively searching. Since it isn't the flavor of the week anymore you don't have as many programmers entering the field as ruby devs.
Mentoring is always a solid option too, the language and frameworks are simple. Any CS graduate worth his degree will pick it up in no time.
You can find more experienced Ruby devs -- finding someone with multiple years of Elixir would be very difficult.