You can spend a year looking for a tank like that and not find one. I hope that you do, but custom tanks like that are rarely sold and traded since they people that ordered them don't typically just buy on a whim.
You can probably find a 180 or 210 pretty easily and on the cheap. ...maybe a 300 deep dimension, but some those have seam and structural issues so be careful if you go to look at one of these.
A 72x36x30 is a $2800 custom tank from customaquariums. Really nice size.