We've got a baby hammock that we plan to have bub sleep in for the first 3mths or so.... before we move to the cot.

Inside the baby hammock is the mattress insert that it came with and over the top of that i've put a small mattress protector around it (it's one of those small ones that fits around the part of the cot mattress where bub's butt would be if that makes sense).
So this will protect the little cushion mattress from any leaks etc however what about sheets?
I don't have any to fit the hammock I realised!! What should I use and those with hammocks what have you done?
I was just going to put a cotton wrap in the hammock for bub to sleep on..... and bub will be wrapped up anyway.

Thank you Just want to protect the hammock & mattress itself from any leaks or spews etc.