Emma, that is actually how I got my first batch in early May. I found out who supplied the Asian market - ends up it was a place called "The Gator Farm" - and contacted them
There are still many catfish that are allowed in Texas, including Channel Catfish. They are native!!!!! It is only some of the exotic non-native species of catfish that are not allowed. Just check another page on that same web site.
and another page on that site even has resources that might be useful when planning your system or buying your fish to stock in it.