For us, flats or prefolds & covers. Never had a leak with them.

Could you grap a pack or 2 of terry flats from the supermarket? With DD I started out with 3 covers. I alternated them, letting them air between uses so I only had to wash them once a day. (purple to pink, air purple, pink to blue, air pink, blue back to purple etc)

Outters of SIO's can be used as covers too