SoHossme ukes come with a strap button on the bottom... most banjo ukes tend to have them built into the tail-piece. Then you just attatch the the other end to the headstock via a lace, or some straps are made to be wrapped around. Or you can attatch a strap button to the heel of the neck, and one to the bottom of the body if needs be.
I can highly recommend Mainland's straps. They're the headstock type too, very good quality, great looking and really good value. I'm in the UK and I got mine in less than a week. Contact Mike (hoosierhiver on the forum) and he'll go above and beyond to help you out. Really great guy!