We use a boosted size 2 bamboozle stretchy with a blueberry coverall. It struggles a bit at the mo with all the extra night feeds my little one is having but havent had to change a sheet yet
...just to add we boost with LL bamboo boosters size 1
I used to use flips at night with DD... Nightime organic insert with a staydry on top... Before we moved to fitteds and wool.
What are you using at the moment? There may be ways to boost what you have??