What do you put in Carrycot? (Besides baby)

I recently bought a stroller with a Carrycot/bassinet attachment for our expected bub but I was surprised that the lining over the mattress is quite rough and synthetic feeling. It definitely needs something between baby and mattress.

So what do you line your carrycot with? I've read about using bassinet sheets but the ones I have (for stokke sleepi mini) are way too big. Are there any brands of smaller/narrower cot sheets? Should I be aiming to get a waterproof mattress protector layer in there as well? The other option I was thinking of was just a sheepskin bunny rug?

I use a flannelette wrap in winter, muslin wrap in summer

I also have a 'pram skin' liner for the stroller attachment when bubs is bigger

What brand is your carrycot? For some brands eg baby jogger, bugaboo you can buy padded liners on eBay with lovely patterns on them and at a fair price :-)

I used to just us a muslin wrap, i had chucky babies so it got changed all the time and was easier to wash and dry in no time.
If you want something warmer and fluffier i've seen people buy those mini sheepskins and use those.

I used sheepskin but my DD was a non-chucker so didn't need to wash it often at all, which was lucky b/c she was a winter born bubs.

Thanks for the suggestions. I went with the uncommon abc designs brand so haven't seen any commercial covers around. I actually tested the bassinet sheet and found its not as big as I thought so might use that plus a terry flat for extra spew catching.