If you are registered, you get access to the members only section, can participate in the buy & sell second hand forum and last but not least you can reserve your preferred username before someone else takes it.
There are a number of straps available new and used. I would recommend KEH (at www.keh.com) for used Hasselblad equipment, if you are nowhere near a local shop. I would assume any Hasselblad dealer would either have them in stock or be able to order them for you. I would not recommend an old used leather strap sight unseen, because if the leather hasn't been properly cared for, the strap can break. There are a number of different straps: