We get our onsies from baby-pants.com and its the t-shirt style. And there around 30.00, and they have the printed or plain style. At home I usually wear the printed, and when we go out in public I wear the plain style. The onsies do hold up the diaper very well, and prevents sagging. They do make diaper changes a lot easier.
We live in Michigan and the weather is not so good. In the winter I have on jeans when we go out with a onsie, and it does make diaper changes hard at times, plus I wear the footed sleepers at night. During the summer months I wear shorts and a onsie while out, and diaper changes are a lot better and easier for her.