there are several smaller species of cat shark that would be better for the average aquarium. the should still be kept in tanks that are at least 6' long. i would say a minimum of a 125g tank. a 180 would be better though.
scyliorhinus retifer-Chain Dogfish grows to a maximum of 18" this one should be fairly common in the trade, but is not.
Atelomycterus macleayi- Marbled Catshark grows to 24". i have seen these on occasion for sale at some distritubors not very common, but a much better choice than the
banded cat shark.
Atelomycterus marmoratus- Coral Catshark grows to about 27". very uncommon in the trade, but a very nice looking shark.
there are others, but i have never seen any on any distributors lists. i do search these out several times a year. i plan on keeping an Elasmobranch tank at some point, so i like to keep track of what is available.
if you are really interested in keeping Elasmobranch's please pick up a copy of Scott W. Michaels "Aquarium Sharks & Rays". fortunately or unfortunately- in most cases it will cure anybody of the thought that they can keep a shark in their system. most of the information if have listed above has come from the book.
G~