Seeking pet CATFISH (EVERETT)

Hello, we have a huge (about 15ft X 6ft) in ground pond with koi, goldfish and dojo loaches that we are seeking to add catfish to.
We haven't been able to find channel or red tail catfish (also interested in any other types that do not require tropical/heated water temperature) at any local stores.
We had Channel catfish in our pond at one of our previous residences and they got HUGE! We were excited to build this pond and be able to have them again so we have been disappointed to not have been able to find any.
We have a tank inside for quarantine and for raising them until they're bigger and ready to survive in the pond, which is where we would be housing any new fish over the winter.
We also may be interested in dojo loaches or other fish that can thrive in an outdoor pond as well as plants for both the tank and the pond.
Thank you!!!