I installed one on the back of a Charger bass boat back in ‘96. Highly recommended. I don’t remember the brand but it was a 2 step that bolted on the top of the back edge and about halfway down the back.
I did a quick google search for “bass boat boarding ladder” and saw one similar to the one I had.
There were a few that came up in my search that bolt to the motor mount that looked like they’d work great with no drilling.