We have a 3 coupler kettle designed to use a sight glass like the kind Bobby sells (BrewHardware). It has the older style welds we've used for the last year or so. We're trying to clear up space (and believe me this thing is huge!) so we're blowing it out. $400 for a 45gal kettle with 3 welded couplers.
http://www.spikebrewing.com/bargain-cave
-SB
http://www.spikebrewing.com/bargain-cave
-SB