Waterproof mattress protectors!

[Krumblina]

I have a Cosatto wow 2 pram and have been given a second hand mokee wool nest.
We also have a Lua bedside cot for overnight.

The lullaby trust say if baby is sleeping they need to be on a firm mattress with a waterproof mattress protector on it.
I can't seem to find protectors to fit prams anywhere! I messaged cosatto but haven't heard back.
If baby is sleeping in the pram then surely it does need a protector and sheets?
With the Mokee wool nest I ordered a new mattress to fit it from baby mattresses online plus 2 waterproof protectors which are supposed to fit the mattress ordered but when I put them on they are massive and baggy so it's not a flat surface.
I tried ordering made to measure ones for the pram too but giving the dimensions of the mattress they've come way too big.
Any ideas? Do I need waterproof protectors for these 2 nap surfaces?
Is the wool nest ok to use second hand if I've got a new mattress for it?
Thanks

I used the hippy chick flat sheet ones. They’re really good. I still use mine on the car seat for the youngest on long journeys

I'll have a look thank you. Do they not have to be as close a match in size then as it's a flat sheet?.

I used a moses basket sheet- the pram mattress size was the same....

Cosatto wow 2?

I put a fitted sheet over the top
https://www.hippychick.com/shop/waterproof-mattress-protector-flat-cotton/?srsltid=AfmBOorSPhdITha1dqKgX8h1KtWBVh20ZAmgHDb-O_I63EVzIFnf7efI