Hemp Jewellery

If not, where can I get hemp and is it expensive?

Make sure the wires you plan to use for making jewelry would be nice to wear for days, and does not disintegrate when wet. Otherwise, if you like how it looks when you think about it, you can use it - you can not call it "hemp" if it is not.
There are many places online to get hemp. You can get a little ball of twine in natural colors for as little as $ 2 plus shipping - more bullets, heavier strings and string color usually run in the $ 5-10 range, plus shipping. Many local craft stores (Michael's, JoAnn, Hobby Lobby, etc.) to win, too.
Try this search for lots more info.
http://www.google.com/search?ie=UTF-8&oe ...
Good luck!

You can use the string to the bosses, but to be "Hemp" jewels really needs to be made from hemp, hence the name.
Try different types of thread and you will see that the thickness of it will change the size of your finished work.