Opening in concrete ceiling for attic ladder too large

We have an opening in our OG concrete ceiling for an attic ladder measuring 140x70cm. We could get a ladder measuring 120x70cm (Roto Designo) cheaply. It has slight cosmetic damage and can no longer be sold.

Is there a sensible way to close the 20cm difference, or do we have to buy a suitable ladder after all?

So far, I had two ideas to reduce the hole size:

[*]Cut wooden beams to size and screw them to the concrete ceiling
[*]Build a suitable formwork and concrete the hole closed

Are there any other ideas or comments?

We have 140x70 and I didn't want it any smaller when carrying a box up the stairs.

I would stick to the 140x70cm if you want to move things up and down more often and maybe sometimes have something bulkier. If it is only the Christmas decorations once a year, then 120x70cm will also do.

We will not store much there. There is hardly any height available, so it is more of an emergency opening to access the attic.

Depending on how and where the staircase is anchored, I would build formwork and drill a few holes sideways into the existing concrete ceiling. Insert some steel rods there to connect the new concrete. Then pour screed concrete from above and let it dry. If the roof above is a cold roof, do not forget the insulation.

We won’t store much there. There is hardly any height available, so it is more of an emergency opening to get to the attic.

I would put more thought into this. Although you say you don't want to store much, is there really enough other storage space available? Does the desire also have something to do with the ability? Can you afford not to have to access the attic? While you are now leaning towards 120 cm length because of the price, others tend towards a proper staircase. As far as I know, a floor hatch is priced in; I would not want to forego the minimum comfort, depending on how much savings or compensation we are talking about. You know, 20 cm can be quite significant :€