You can always buy some fabric and dye it. I bought a lavendar color fabric and added 1/2 part black dye and 1/2 part denim blue dye, and also on another I just used the 1 part denim blue dye. Im torn between which one to go with :confused :facepalm. Just make sure that if and when you buy some fabric (I got mine for $2 a yard) to buy a 1/2 yard extra to experiment with the different mixtures of dye.
Quite honestly, most people get a light blue or dark blue cotton duck/broadcloth and go from there with the dyeing. Most off-the-self jumpsuit/coverall is made of the same fabric. Its like a light jeans fabric.
After spending hours and hours searching fabric stores, with no luck.. I am leaning towards calling the fabric a twill / bottomweight fabric that is periwinkle in color. So if one finds some periwinkle in a bottomweight fabric they could use Green Peppers Jumpsuit pattern found at Seattle Fabrics.