Katrina's soaker patterns can be easily modified to make side-snapping (or velcro) covers.
All you do is extend the sides of the body piece about 3/4" at the sides. Then you don't sew the leg and waist pieces all the way to the ends, and just fold over the edges of the body piece so you have the thicker edges for applying snaps.
Then just apply your snaps or velcro.
Go Hawks! ;)
Sea-hawks.... I have mentioned I am in Seattle before, right? ;)