As far as building your own volume pedal, check out any DIY effects forum/site and there should be a decent schematic for it, including a parts list sometimes.
For EB parts you'll need to go through Strings n Things, EB's distributor over here. Beware though - these guys (EB) charge the earth for the smallest components. I was after a 500k vol/tone, a 5-way and a 3-way switch and this would've set me back nearly £50!