The closest parallel example would be a very crunchy hippie. A junkadoon does not carry the same values as a hippie, just the crunchiness. They are often homeless and always dirty. Their appearance is part punk, part hippie, part homeless. Imagine a backcountry hippie thats lost its value. They will often have extreme tattoos/piercings, strangely cut/colored hair, and can be found loitering in dirty cities. As far as fashion goes, overalls are preferred. They often are found playing music in the streets for money.
Once you see one for yourself, you will know it. That is a Junkadoon.