Most internet shops sell picks. StringsDirect have a good selection. I prefer the oversized triangular variety - I find them easier to hold onto. (I'm not a natural plectrum player, and I find that I need to grip small pleckies too hard to allow freedom of wrist movement.) The sharper triangles seem to give a better attack than the more rounded "Fender" shape. Usually I use .88 or 1.00, but I've got a 2mm as well which gives extra volume at the expense of tone.