You could get a Ford's boa and house it in a 20 gallon long. The boa would cost you the most. Or buy a 75 gallon aquarium ($50-$100 on craiglist) and cover the top with some saran for humidity (no heat on the saran wrap though). The second way you could get a much bigger boa - my 5 1/2 foot JCP does well in a 75 gallon tank.