Fakro ladders
You probably could get them to fit the standard opening, same as the Stira ones, not sure, ours went in before the ceiling so it wasn't a consideration for us.
I can't rightly remember the cost but it was a good bit cheaper than the same size Stira, carpenter advised not to get Stira as simply paying for the name "as seen on the Late Late Show" etc
L shaped pole which fits in a square hole, twist pole and the trap door lowers on a spring so that you can then unfold the three hinged sections to lock.
There is also a handrail on the steps