Who needs Levis when you can do it yourself!?
There is quite a few places you can buy studs, I got these ones from this seller on ebay. They come in packs of 100pcs and work out to about £2.52 which is quite a good price. The seller is based in Hong Kong so they did take about 4 weeks to arrive but postage is free so you can't really complain! There are lots of other types of studs on ebay, and they can be used for clothes, shoes, bags.. anything really!
I also bought the shorts from ebay (not sure of the seller) for £12 (River Island shorts).
As you can see I haven't finished them yet, simply because I ran out of studs! Which is annoying as I'll now have to wait another 4 weeks to finish them so if you do decide to order them I'd suggest getting two packs (I've just ordered another two!). You get the idea though, I'm only planning to cover the one side I've started. The studs are really easy to use and can be taken off without damage quite easy if you make a mistake or just change your mind. They came in this cute little box and a sealed plastic bag. I will post a picture of the shorts once they are finished!