UPS to fit in (shallower) wall mounted rack

I'm looking for a UPS that can fit into a wall mounted rack that is ~25cm deep between posts (and to allow for wires).

I have an existing old desktop APC Smart-UPS 700 which has a management card (the card cost me more than the UPS) so have been looking at rack mounted APC units so I could re-use the management card. All the units I can find are too big for the rack as far as I can see.

That said I'm not against getting something different so all suggestions welcome.

I've read that 2U is better than 1U due to being more standard batteries although beggars can't be choosers right now :-)

I'm in the UK and will be probably looking to buy something second hand if that makes a difference.

And here's the rack if that helps? https://imgur.com/a/81zolDV

Thank you very much in advance :-)