Stern-mount access ladder for 1973 C&C 25

Hi - seeking a transom mount ladder for 1973 C&C 25’ in GHTA (ON) as portable rope type no longer suits; we have an outboard motor, so only have 12" width available beside the rudder. Want to be able to access folding it down from in the water should we fall off. Features best to have? Treads vs. round rungs? Grade of stainless steel? Thanks - launching in a week