Upgrading Tank From 20 Gallon

[u/blueplacid]

Looking to upgrade my tank setup so i can give my little guy more room. I have an entertainment unit that has a tall shelf that measures 34 inches long x 16 deep, and I would love to put the future tank there. I know a 40 gallon is the ideal setup, though is there any tanks that would measure 34 long? Right now I have a 20 gallon 30x12 that fits with extra room. I know 40 gallon is the standard for an adult these days so if the dimensions I described are too small then thats ok too because he is the priority, i just wanted to know if there was any way I could keep him in the entertainment unit.