Happy to hear you are wanting to make some real bows. I agree with others that you can still find some local wood. I worked in Northern Illinois, Grayslake area for a summer doing bat surveys in those buckthorn infested forest preserves. I remember keying out a huge number of tree species, many of which would qualify as good bow wood, in some of the more mature forests. Not encouraging you to cut without permission on forest preserves, but there are a number of those remnant forest patches out there and not are all county forest preserves. Try knocking on farmhouse doors, and if you have a bow, show it to them, that usually opens up the conversation.