This answer over at eTrailers confirms what you said:
https://www.etrailer.com/question-352790.html
Q: Our remote that lifts tv got broken. Can we buy a new remote
A: The Lippert Components TV Lift System with RF Remote # LC309690 will use the replacement remote and controller # LC253395. It is only available with the remote and the controller as a kit from the manufacturer
They sell the controller & remote package for $315:
https://www.etrailer.com/p-LC253395.html
I can't believe they won't sell just the remote, but they probably burn the remote's code into the controller, so it's just easier this way and they don't mind making you spend hundreds of dollars for a $20 remote.