So you want a whole kit, with
tanks, batteries, cartos, etc? Or by
tank system do you mean carto+tank?
If you don't mind buying a tank separately from a battery, you cannot go wrong with Ibtanked:
IBTanked - Get Tanked With Us!
They have 19mm and 25mm tubes, standard and Xl length. If you get the plastic caps they whole tank is super cheap, with Stainless Steel (I'd suggest you go this way) the whole tank is about $24 IIRC. You still need Cartos though.
Awesome tanks, I just wished they flame polished the ends of the glass tube and ran it through a kiln cycle after cutting. Actually I have no idea if they run it through a kiln after cutting, but I'd assume no since they didn't go to the trouble of flame polishing the ends. They likely don't have access to glassworking equipment and are either just buying the tubes pre-cut, or just buying long tubing and cutting it down, followed by a smooth grinding of the ends.