Questions about Mamas and Papas toddler bed

[3become4]

Wasn't really sure where to post this but hope someone can help...

So I've inherited an old Mamas and Papas toddler bed (can't find anything that looks like it on their website) for DD. The first problem is it has a broken slat. I assume this is easy to fix but any ideas how best to go about it? Secondly, I was planning to buy a Mamas and Papas cotbed (size 400) mattress for it. But the mattresses measure 139cm L x 69cm W. The bed is 139cm L but measures 67cm between the side rails. Will the mattress squeeze in do you think?

Or shall I just buy a new bed and mattress from John Lewis (which all seem to measure 140cm x 70cm!)?!

Is it this one? www.hotukdeals.com/deals/mamas-papas-junior-bed-white-now-39-99-argos/912986

You can repair a slat by just buying a similar thickness of wood at a diy store and cutting to size.

I have this bed and just use a standard 140 x 70 mattress. Babymattresses online sell cheaper but high quality mattresses (I have no connection to them). Use code TWINSAVE for 10% off.

Thanks but it isn't that one. It's pine and has side rails on both sides. If it wasn't for the side rails I would definitely buy the mattress but I'm worried it won't squeeze in.