with big purchases like the meter, make dam sure that it has warrenty and comes from a reliable source, because more than likely u'll need it. getting one for cheap off ebay may seem appealing, but they might not want to cover warrenty. and if they do, it'll take you a long time to ship anything back and get it replaced.
visit ur local hydro store, see what they have, or visit a weld/fab supplyer like acklyn-grainer for the regulator n tank.
otherwise, just google it and look for the best deal