Check out medical supply stores, the kind that sell wheelchairs and medical uniforms, or look for a uniform store in your town, those two places are ware I used to get scrubs (or goodwill in Halloween season). Even wallmart has had scrubs. But white is out of fashion and so are the long ones. If those don’t work check out the local fabric store and look for scrub patterns or a nurse costume in the pattern catalog.
I dont think it's a coat, it's a dress or smock in the old style, they never wore them at work I only seen a box of them when I cleaned out a store room and I took one home with the gieger counter and...
a little search and some sites recomend using a A Line dress pattern and shortening the hem and adding the collar
Nurses ewwwwwww been there done that, any aunt in nursing school wont get a call back