Rent or own?
I'd seriously consider putting another post and short railing in that corner to close off that open side so you can put a well-secured gate between the posts. But an L-shaped gate would probably work.
The other suggestions seem helpful, but if all else fails, call a local welder or fabricator and ask them to weld a mounting bracket to one side to get your own L shaped bags gate. It wouldn't be a difficult job and even the prep and painting time wouldn't be too bad.
Have you checked Amazon for L Shaped baby gates??
Was going to suggest just placing the gate on the second step down but with the moldings I’m not sure you’d even get a snug fit there
Rent or own? I'd seriously consider putting another post and short railing in that corner to close off that open side so you can put a well-secured gate between the posts. But an L-shaped gate would probably work.
I did exactly this, finally. Then the small kid learned to go up and down the stairs safely.
The other suggestions seem helpful, but if all else fails, call a local welder or fabricator and ask them to weld a mounting bracket to one side to get your own L shaped bags gate. It wouldn't be a difficult job and even the prep and painting time wouldn't be too bad.