There is a 20-gallon extra high, it has the same foot print as a ten-gallon, but is twice the height. I paid $70 for mine. No, Petco does not carry this size.
Not too long ago, I made a tank. I bought a used 5-gallon and applied a silicone de-bonding agent called Lift-Off to it. I cleaned the parts all up and used the frames and the bottom plate of glass to build the new tank. I went to my local hardware store and bought four panes of glass that had the same lengths as the old panes, but these new ones are twice the height. I used silicone and glued all the parts together, so now I have a 11 gallon tank with a 5.5-gallon foot print. You could do the same, but I would get thicker glass then what a hardware store has to offer.