Thanks to Angela for this Frugal Baby Tip!
I've seen patterns made by Simplicity (diapers and covers, but the covers look like fashion covers, but I'm not entirely sure). Kwik-sew has two patterns, one has fitted diapers and covers the other has diapers and a t-shirt, I think. Sew-baby has a Snap-Happy Cover.
Yesterday, I took three covers (Dappi, Diaperrap and Air-Flow) and an Indisposable small. After stretching them all out I decided to go with the Indisposable. Laid it out on a piece of paper and traced along one side... after adding 1-2 inches in length, I folded the paper in half and cut out the pattern. I sewed it all up and it fits great! I still need to add elastic to the legs to get a true fitted diaper, but I gave it a trial run last night. I'm so excited, I layered it inside a MotherEase Popolino, and pinned it. The MotherEase Popolino was completely dry on the back and damp on the front, woohoo!
And the materials I used were two layers of terry, sandwiched between one flannel on outside and a cut up flat fold on the inside. If I can do it anyone can!